/Sandeivon 

^wilci^oard^ 

for 

RJletiiaiina-Curteni 
Povret  ^aiioap 


1,- 


Switchboards 

For 

Alternating-Current 
Power  Stations 


C.  H.  Sanderson 


Switchboards 

For 

Alternating-Current 
Power  Stations 


C.  H.  Sanderson  and  H.  A.  Travers 
General  Engineers,  Switchboard  and  Power  Station  Design 

Westinghouse  Electric  & Mfg.  Co. 


Reprinted  (revised)  from  The  Electric  Journal 
Vol.  X,  No.  1 and  Subsequent  Issues 


Westinghouse  Electric  & Manufacturing  Company 
East  Pittsburgh,  Pa. 


Publication  1541-A— 3-16 


Digitized  by  the  Internet  Archive 
in  2016  with  funding  from 

University  of  Iliinois  Urbana-Champaign  Aiternates 


https://archive.org/details/switchboardsswitOOtrav 


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INTRODUCTORY 

The  favorable  impression  made  by  the  series  of  articles  herewith 
reproduced  has  been  taken  as  justification  for  publishing  them  in  a 
convenient  form  for  the  benefit  of  those  interested  in  modern  switch- 
board practice.  Owing  to  the  considerable  progress  in  various 
branches  of  the  art,  some  of  the  subject  matter,  particularly  concern- 
ing circuit-breakers,  required  revision  in  order  to  bring  the  informa- 
tion to  date. 

The  cost  data  is  reproduced  from  the  original  and  it  should  be 
recognized  that  changes  in  practice  may  involve  changes  in  costs  so 
that  the  data  should  be  limited  in  use  to  purposes  of  comparison 
only.  In  general,  this  publication  is  not  intended  to  be  a technical 
bulletin  on  switchboards,  and  the  Company  is  not  responsible  for 
possible  inaccuracies  in  the  information  which  it  contains. 

In  order  to  further  enhance  the  value  of  this  publication,  a con- 
siderable amount  of  information  has  been  added  in  the  form  of  cuts 
illustrating  switching  apparatus,  switchboards,  and  switch  structures 
for  various  classes  of  service. 


SUMMARY 


Page 

Classification  of  Switchboards 5 

Classification  of  Circuit-Breakers 13 

Essential  Operating  Features 15 

A.  C.  Generator  Panels 19 

Feeder  Panels  for  Power 22 

Load  Panels 23 

Synchronous  Motor  Panels 23 

Line  Panels 25 

A.  C.  Rotary  Converter  Panels 26 

D.  C.  Exciter  Panels 27 

Comparative  Space^  Required 27 

Comparative  Cost 27 

Self-Contained  Switchboards 29 

Application 29 

Choice  of  System 31 

Choice  of  Apparatus • 32 

Choice  of  Panel  Design 38 

Arrangement  of  Apparatus 46 

Costs 47 

Rear  of  Board 48 

Remote-Mechanically-Controlled  Switchboards 51 

Advantages 53 

Application 56 

Types 57 

Circuit-Breaker  Structure 63 

Structure  Arrangements 72 

Costs 74 

Details 80 

Electrically-Operated  Switchboards 84: 

Panel  Control  Board 86 

Control  Desk 87 

Control  Pedestals  and  Posts 90 

Miniature  Bus 92 

Synchronizing  Devices 96 

Other  Control  Equipment 98 

Signal  Equipment 99 

Circuit-Breaker  Structure 107 

Examples  of  Westinghouse  Circuit-Breakers  and  Switchboards 123 


SWITCHBOARDS  FOR  ALTERNATING-CURRENT 
POWER  STATIONS 

C.  H.  SANDERSON 

General  Engineer,  Switchboard  and  Power  Station  Design,  Westinghouse  Electric  & Mfg.  Co. 

There  are  three  distinct  classes  of  switchboards  which  are 
suitable  for  alternating-current  stations: — The  “self-contained” 
panel  type,  hereinafter  called  “Class  1,”  the  “remote  mechanically 
controlled”  called  “Class  2,”  and  the  “electrically  operated,”  called 
“Class  3.” 

Class  1 includes  those  switchboards  in  which  all  apparatus  is 
mounted  on  the  panels;  Class  2,  those  in  which  the  main  current- 
carrying  parts  are  mounted  apart  from  the  board  with  main  switch- 
ing devices  mechanically  controlled  by  means  of  levers-on  the  panels; 
Class  3,  those  in  which  the  switching  devices  are  operated  by  sole- 
noids or  motors,  or,  in  a few  cases,  by  a combination  of  solenoids  and 
compressed  air,  known  as  electro-pneumatic  operation.  The  classes 
are  illustrated  in  Figs.  1,  2,  and  3. 

The  question  often  arises  as  to  the  dividing  line  between  these 
three  classes.  This  can  only  be  answered  in  a general  way.  There 
are  many  instances  in  which  but  one  of  the  three  classes  seems  ap- 
plicable. There  are  also  many  instances  in  which  any  one  of  the 
three  could  be  applied  with  good  results.  In  a large  number  of  in- 
stances, however,  the  advantages  are  so  equally  balanced  that  the 
dividing  line  becomes,  in  reality,  a broad  belt  of  uncertain  width, 
increasing  in  advantage  for  one  class  or  the  other  near  the  edges. 

The  principal  factors  influencing  a choice  of  one  over  the  other 
two  classes  are: — Power  to  be  handled,  essential  operating  features, 
space  required,  and  permissible  cost.  A comparative  discussion  of 
the  three  classes  as  regards  these  factors  may,  therefore,  be  of  some 
assistance  to  those  who  have  to  make  a choice. 

Capacity  to  Be  Handled 

The  capacity  of  a station  determines  the  class  of  switching 
devices  which  may  be  used,  which,  in  turn,  usually  determines  the 
class  of  switchboard  to  be  employed.  Oil  switches  and  circuit- 
breakers  are  given  an  ultimate  breaking  capacity  rating  just  as 
they  are  given  a current  and  voltage  rating.  These  ratings  are 
determined  by  three  characteristics ; namely,  the  insulation  for  a given 
voltage,  the  size  and  arrangement  of  the  current-carrying  parts  for  a 
given  current-rating,  and  the  ability  to  withstand  the  severe  mechani- 


6 


Switchboards  For  Power  Stations 


1541 


Fig.  1— Switchboard  of  Self-Contained  Type  (Class  No.  1)  for  Two  Exciters,  Three  Genera- 
tors, and  Two  Feeders 


All  Apparatus  except  rheostats  mounted  directly  on  panels. 


1541 


Switchboards  For  Power  Stations 


7 


Fig.  2 — Mechanically-Operated  Remote-Control  Switchboard,  Class  No.  2 


All  alternating-current  control  apparatus  is  mounted  apart  from  the  switchboard. 
When  this  class  of  board  is  of  the  remote-control  self-supporting  type,  the  apparatus  can 
be  mounted  on  a separate  framework,  apart  from  the  board,  and  can  be  located  in  a 
separate  room  above,  below  or  behind  the  switchboard,  the  distance  being  limited  by  the 
weight  and  inertia  of  the  mechanical  connections  to  the  circuit-breaker. 


8 


Switchboards  For  Power  Stations 


1541 


cal  stresses  due  to  the  explosive  effects  of  short-circuits.  The  ulti- 
mate breaking  capacity  of  a circuit-breaking  device,  therefore, 
depends  primarily  on  the  dimensions  and  proper  association  of  those 
parts  which  must  bear  the  stresses  due  to  opening  under  short- 
circuit.  The  amount  of  power  which  the  circuit-breaker  set  for 
instantaneous  tripping  must  interrupt,  in  case  of  short-circuit,  is 
not  that  indicated  by  the  nominal  rated  capacity  of  the  station,  but 
the  maximum  power  which  the  generators  are  capable  of  delivering 
at  the  instant  the  circuit-breaker  opens.  Modern  high-speed  gener- 
ators give  from  ten  to  twenty  times  full-load  current  for  the  first  few 
cycles  of  a short-circuit.  Some  manufacturers  permit  even  higher 
values,  instances  of  fifty  times  full-load  current  on  short-cir  cuit  being 
reported. 


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Fig.  3 — Electrically-Operated  Remote-Control  Switchboard,  Class  No.  3 

This  board  is  arranged  for  controlling  one  more  generator  than  the  board  shown  in 
Figs.  1 and  2,  but  the  switchboard  is  much  shorter.  The  remote-controlled  structure 
for  switchboards  of  this  type  and  capacity,  when  similar  switching  equipment  is  used, 
looks  very  much  like  the  remote-controlled  structure  shown  in  Fig.  2.  The  electrically- 
operated  board,  however,  is  usually  of  much  greater  capacity  than  either  of  the  other  types 
and  the  switching  equipment  is  therefore  usually  mounted  in  separate  masonry  or 
concrete  compartments. 


The  catalogue  breaking  capacity  of  a circuit-breaker  is  usually 
expressed  in  terms  of  the  total  rated  capacity  of  the  generating  and 
synchronous  apparatus  on  the  circuit  on  which  the  breaker  can  be 
used  under  specific  conditions.  The  apparatus  rating  used  should 
be  the  maximum  load  at  which  full  voltage  can  be  maintained  so 
that  overload  capacities  of  one  hour  or  more  should  be  included. 
The  breaking  capacity  rating  of  a given  circuit-breaker  for  a gi\T'ii 
case  varies  with  the  conditions  that  may  limit  the  short-circuit  current. 


1541 


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10 


Switchboards  For  Power  Stations 


1541 


The  basis  of  rating  circuit-breakers  is  purely  arbitrary  and  the 
actual  characteristics  of  the  machines  and  circuits  must  be  known  in 
order  to  modify  the  assumptions  so  as  to  secure  a correct  application 
of  a given  circuit-breaker  to  a given  condition.  The  following  are 
the  assumptions  upon  which  the  ultimate  breaking  capacity  of  a 
circuit-breaker  are  based  by  a leading  manufacturer.  Any  departure 
from  these  will  change  the  relative  rating. 

1.  That  the  generators  have  an  inherent  reactance  of  approxi- 
mately 8 per  cent  or,  in  other  words,  give  a maximum  current  on  the 
first  wave  of  short  circuit  of  12.5  times  the  root-mean-square  full-load 
current ; and  also  that  the  sustained  short-circuit  current  has  a maxi- 
mum value  of  three  times  the  r.m.s.  full-load  current. 

2.  That  the  current  at  the  time  the  circuit  is  opened  is  approxi- 
mately 50  per  cent  of  that  occurring  on  the  initial  wave;  or  in  other 
words,  6.25  times  the  r.m.s.  full-load  current. 

Current  Trans. 

r-r-r—r-r;:;. 

H H 

Feeders 

-Single  Bus  System 

Used  for  small  stations  where  simplicity  and  economy  are  of  primary  importance. 

3.  That  the  circuit-breakers  are  very  close  to  the  generators  or 
other  source  of  power,  so  that  the  circuit  reactance  from  the  gener- 
ators through  the  circuit-breakers  to  the  point  of  short-circuit  is 
practically  negligible. 

4.  That  the  operation  of  the  circuit-breakers  is  normal  for  the 
particular  tyf)e,  and  that  the  method  of  tripping  is  that  known  as 
“instantaneous”,  under  which  conditions  the  mechanism  should  be 
expected  to  operate  in  0.1  to  0.2  seconds. 

5.  That  the  normal  operating  voltage  which  the  circuit-break- 
ers are  called  upon  to  open  is  that  on  which  their  rating  is  based. 

6.  Where  a circuit-breaker  is  used  on  a lower  voltage  than  the 
maximum  for  which  it  is  designed,  it  is  assumed  that  an  increase  of 
approximately  1 per  cent  in  kilovolt-ampere  rupturing  capacity  is 
permissible  for  every  1 per  cent  decrease  in  operating  voltage. 

The  amount  of  current  available  in  a given  circuit  under  short- 
circuit  conditions  is  determined  by  the  amount  of  effective  impedance 
(usually  nearly  all  reactance)  in  the  circuit.  Additions  to  the  effec- 
tive reactance,  whether  introduced  by  transmission  lines,  power 


1541 


Switchboards  For  Power  Stations 


11 


transformers,  or  otherwise,  will  reduce  the  available  current  in  direct 
proportion. 

When  circuit-breakers  are  to  be  used  on  a secondary  of  a step- 
down  transformer,  the  kva.  capacity  of  which  is  small  in  comparison 
with  that  of  the  source  of  supply,  the  reactance  of  the  transformer 
and  its  capacity  are  the  factors  to  be  considered  in  determining  the 
size  of  breaker  to  be  applied. 

Oscillograph  records  show  that  the  first  rush  of  current  on  a 
short  circuit  falls  off  to  approximately  two  or  three  times  full-load 
current  at  the  end  of  one  and  one-half  to  two  seconds.  As  this 
current  value  is  approximately  one-half  of  that  assumed  to  be  flowing 
at  the  instant  an  instantaneous  trip  breaker  would  open,  a circuit- 
breaker  provided  with  relays  having  a definite  minimum  time  setting 
of  two  or  more  seconds  may  be  used  on  a circuit  having  twice  the 
capacity  rating  of  that  breaker  when  set  to  trip  instantaneously. 


I^^Current  Trans. 


— 1 

I I 

— — r 

, 1 

i i 

i . 

: Tt 

i i , 

Bos  A 
Bus  B 
Dis.  Sw. 


Oil  Cit  Br. 


V 


Fig.  6 — Double-bus  Single  Circuit-Breaker  System 
This  arrangement  greatly  increases  the  chances  for  continuity  of  service  over  that 
shown  in  Fig.  1.  One  bus-bar  may  be  used  as  an  auxiliary  only,  or  one  may  feed  a lighting 
load  while  the  other  feeds  a power  load. 


A non-automatic  breaker  may  be  applied  on  a circuit  of  twice  the 
capacity  of  the  corresponding  automatic  instantaneous  trip  breaker 
as  at  least  two  seconds  will  elapse  before  the  station  attendant  can 
trip  the  breaker. 

The  breaking  capacity  of  a circuit-breaker  may  be  expressed  in 
terms  of  the  maximum  current  which  the  breaker  is  capable  of  open- 
ing successfully  at  its  rated  voltage.  This  maximum  value  of  current 
which  a breaker  will  open  on  short  circuit  at  its  rated  voltage  or  at 
any  given  service  voltage  may  be  designated  as  the  ultimate  ampere 
breaking  capacity  of  a breaker  and  is  obtained  as  follows: 

(a)  Find  the  current  corresponding  to  the  catalogue  kva. 
breaking  capacity  rating  given  for  the  breaker  under  the  voltage 
required. 

(b)  Multiply  this  current  by  6.25  (the  second  assumption  given 
above  is  that  the  current  at  the  time  the  circuit  is  opened,  is  50  per 
cent  of  that  occurring  on  the  initial  wave.) 


12 


Switchboards  For  Power  Stations 


1541 


If  the  product  thus  obtained  is  less  than  the  current  available 
under  short  circuit  conditions  in  the  circuit  on  which  a breaker  is 
to  be  applied,  a larger  circuit-breaker  should  be  selected. 

This  latter  basis  of  rating  is  the  more  satisfactory  one  as  it  forms 
a statement  of  what  the  breaker  is  actually  capable  of  doing  without 
reference  to  the  capacity  of  the  power  system,  method  of  tripping 
the  breaker,  to  the  short-circuit  characteristics  of  generators  and 
other  synchronous  apparatus,  or  to  the  reactance  of  apparatus  and 
circuits  up  to  and  beyond  the  breaker  to  the  point  where  the  short 
circuit  occurs. 

Reactance  Coils — By  the  use  of  current  limiting  reactance 
coils  at  various  points  in  the  system  it  is  possible  to  use  circuit-break- 
ers having  a catalogue  rating  less  than  the  capacity  of  the  system.  It 
may  be  advisable  in  some  cases  to  use  the  combination  of  reactance 
coils  and  small  circuit-breakers  rather  than  a large  breaker  because 
of  space  and  cost  considerations  and  also  to  reduce  the  strains  on  all 
parts  of  the  system  due  to  a great  rush  of  current  to  a short  circuit. 
Moreover,  without  the  use  of  the  coils  there  is  always  present  the 
danger  that  a heavy  short  circuit  will  open  up  the  main  circuit- 
breakers,  instead  of  the  individual  feeders  affected,  thus  shutting 
down,  possibly,  an  entire  system.  It  is  this  elimination  of  service 
interruption  obtained  by  the  use  of  reactance  coils,  cutting  out  only 
the  feeder  affected,  which  makes  for  ideal  operating  conditions. 

Reactance  coils  are  frequently  placed  in  the  generator  circuits 
to  limit  the  flow  of  current  on  short  circuit  and  thereby  to  decrease 
the  harm  done  to  a machine  from  internal  short  circuit  by  the  re- 
maining machines  connected  to  the  bus-bars,  as  well  as  to  limit  the 
station  output  in  case  of  external  short  circuit.  This  disposition  of  the 
reactance,  however,  does  not  eliminate  the  drop  in  voltage  on  the  sys- 
tem caused  by  a short  circuit,  does  not  provide  the  maintenance  of 
service  feature  above  mentioned,  and  does  not  materially  decrease 
the  strains  on  the  circuit-breakers. 

The  ideal  location  of  these  coils  is  shown  at  A,  Fig.  14.  If,  how- 
ever, the  cost  is  prohibitive  or  space  will  not  permit,  coils  may  be 
located  at  B,  which  will  protect  the  group  of  feeders.  The  third 
choice  would  be  to  locate  them  at  C or  at  D.  The  protection  afforded 
to  the  apparatus  and  service  is  plainly  different  for  the  various  loca- 
tions, and  each  case  should  be  considered  individually. 

Classification  of  Circuit- Breakers — The  usual  classification 
of  circuit-breakers  in  general  commercial  use  is  shown  in  Table  I. 


1541 


Switchboards  For  Power  Stations 

TABLE  I 


13 


Cost 
Per  Cent 

Ultimate 

Volts 

Amperes 

Kva. 

Capacity 

Type 

Design 

Swbd.  mtd.  or  remote 

7 

4500 

200-300 

3500 

mechanical  control 

10 

13200 

300 

3000 

9 

7500 

300-500 

3500 

12 

4500 

600 

3500 

Switchboard  mounted 

13 

13200 

500 

4500 

remote  mechanical 

Single  frame.  Single 

17 

4500 

800 

4500 

control  or  electrical- 

tank for  all  poles. 

30 

13200 

1200 

9000 

ly  operated 

37 

7500 

1600 

8000 

43 

7500 

2000 

6000 

16 

7500 

300-500 

4000 

Swbd.  mtd.  or  remote 

20 

4500 

600 

4000 

mech.  control.  Dou- 
ble Throw 

31 

22000 

300 

6000 

Swbd.  mtd.,  remote 

29 

16500 

600 

8000 

mechanical  cont.  or 

Single  frame.  Separate 

35 

22000 

300-600 

10000 

elec,  operated 

tank  for  each  pole 

18 

13200 

300 

6000 

18 

7500 

500 

6000 

20 

4500 

600 

6000 

16 

22000 

300 

16000 

~ 

48 

16500 

600 

18000 

Remote  mechanical 

Each  pole  a separate 

60 

13200 

1200 

20000 

control  or  electrical- 

unit with  its  own 

67 

7500 

1600 

24000 

ly  operated 

frame  and  tank.  De- 

76 

4500 

2000 

30000 

signed  for  wall  or  pipe 

96 

750 

3000 

20000 

mounting 

55 

22000 

300-600 

40000 

67 

22000 

1200 

35000 

87 

16500 

1600-2000 

40000 

46 

22000 

300 

16000 

48 

16500 

600 

18000 

60 

13200 

1200 

20000 

Remote  mechanical 

67 

7500 

1600 

24000 

control  or  electrical- 

Each pole  a separate 

76 

4500 

2000 

30000 

ly  operated 

unit  with  its  own 

66 

22000 

300-600 

40000 

frame  and  tank.  De- 

73 

22000 

1200 

35000 

signed  for  cell  mount- 

92 

16500 

1600-2000 

40000 

ing 

no 

22000 

600-1200 

80000 

152 

16500 

1600 

80000 

Electrically  operated 

160 

22000 

2000 

100000 

181 

16500 

3000-4000 

100000 

100 

15000 

600 

40000 

120 

15000 

1200 

35000 

Single  frame  or  base  for 

139 

22000 

600 

70000 

Electrically  operated 

operating  mechanism. 

168 

22000 

1200 

65000 

Separate  tank  per 

175 

15000 

2000 

60000 

pole.  Cell  mounting 

280 

2500 

3000 

60000 

55 

35000 

300 

17500 

61 

45000 

300 

20000 

Remote  mechanical 

Each  pole  a separate 

122 

70000 

300 

25000 

control  or  electrical- 

unit. Designed  for 

77 

45000 

300 

30000 

ly  operated 

pipe  frame  or  floor 
mounting 

90 

44000 

300-600 

40000 

125 

66000 

300-600 

50000 

Remote  mechanical 

Each  pole  a separate 

195 

88000 

300-600 

50000 

control  or  electrical- 

unit. Designed  for 

310 

110000 

300-600 

60000 

ly  operated 

open  mounting  on 

620 

165000 

300 

60000 

floor 

200 

22000 

1200 

200000 

Elec. 

oper. 

Single  base.  Separate  tanks.  Reactance 
coil  per  pole.  Cell  mounting 

550 

110000 

300-600 

200000 

Elec. 

oper. 

Each  pole  a separate  unit.  Reactance 
coil  per  pole.  Designed  for  open 
mounting  on  floor 

^Approximate  relative  cost  for  3-pole  circuit-breakers  without  relays  or  transformers, 
t Refer  to  page  10  for  assumptions  upon  which  the  kilovolt-ampere  ratings  are  based. 

The  last  two  designs  given  in  the  above  table  are  known  as  the  reactance  type  breakers.  Their 
great  ultimate  breaking  capacity  is  obtained  by  opening  the  circuit  on  reactance  coils,  by  means 
of  an  auxiliary  contact,  just  before  the  main  contacts  open.  There  is  no  apparent  reason  why 
this  type  of  circuit-breaker  cannot,  by  properly  proportioning  the  reactance,  be  made  to  open 
any  capacity  safely. 


14 


Switchboards  For  Power  Stations 


1541 


Rating  of  Switchboards — The  capacity  which  a switchboard 
will  safely  handle  depends  upon  the  capacity  of  the  circuit-breakers 
employed,  and  the  association  of  the  various  items,  circuit-breakers, 
bus-bars,  instrument  transformers,  interconnections,  etc.,  which 
comprise  the  switch  equipment.  Experience  has  demonstrated 
that  there  are  certain  limits  of  capacity  above  which  automatic  cir- 
cuit-breakers should  not  be  mounted  directly  on  switchboards. 
These  limits  vary  considerably,  according  to  the  conditions  of  the 


— r 

— T 

— — T 

— — T 

— ~T 

^ 1 

<!  1 

1 1 

^ 1 

i i 

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ww  ^ - Uls. 

???  V V V " 

Feeders 

Generators 

Fig.  7 — Double-Bus,  Double  Circuit- Breaker  System 

This  arrangement  gives  the  same  advantage  as  Fig.  6,  with  double  assurance  against 
shut  down  from  circuit-breaker  trouble. 

installation,  but  in  general  it  is  recommended  that  no  circuit-breaker 
in  capacities  above  800  amperes,  or  above  2500  volts,  be  mounted 
directly  on  the  switchboard  and  that  no  self-contained  type  of  board 
be  employed  for  a station  whose  capacity  is  more  than  3000-k.v.a. 
three  phase. 

The  remote  mechanical  control  switchboard  is  limited  in  capacity 
by  the  physical  rather  than  the  electrical  characteristics.  Practically 


Fig.  8 — Ring-Bus  System,  Bus  Sectionalized 

Suitable  for  stations  of  medium  size  where  great  flexibility  and  maximum  economy 
in  cost  is  desired.  This  arrangement  requires  a very  small  amount  of  copper  in  the  bus- 
bars. 

all  high-capacity  circuit-breakers  are  arranged  for  mechanical  as  well 
as  electrical  operation,  but  the  mechanical  control  switchboard  is  con- 
fined to  the  use  of  those  circuit-breakers  whose  size  is  such  that  the 
individual  mechanical  parts,  and  the  mechanical  arrangement  as  a 
whole,  conform  with  good  engineering  practice.  Therefore,  it  is 
recommended  that  this  type  of  switchboard  be  confined  to  the  use  of 
circuit-breakers  of  3000  amperes  or  less,  and  of  35000  volts  or  less, 
and  to  stations  whose  capacity  does  not  exceed  25000-k.v.a.  3-phase 
The  electrically  operated  board  is,  of  course,  unlimited  as  to  capacity. 


1541 


Switchboards  For  Power  Stations 


15 


Essential  Operating  Features 

The  capacity  of  a power  station,  present  and  future,  having  been 
determined,  the  next  step  is  the  decision  as  to  the  number  and  size  of 
. units  to  be  used,  and  the  scheme  of  switching  connections  which  will 
give  the  desired  operating  features.  Figs.  4 to  17  illustrate  a num- 
ber of  the  more  important  and  more  commonly-used  arrangements 
with  explanations  of  their  principal  features.  A single-line  diagram 
of  the  main  connections  should  be  made,  similar  to  one  of  these 
shown,  with  every  machine,  transformer  and  feeder  shown  con- 
nected in.  This  diagram  will  serve  as  a basis  for  the  switching 
equipment  specifications. 


Outgoing  Lines 


Outgoing  Lines 


Da.  Sw. 


Local  Feeders- 

Fig.  9 — Single  Sectionalized  Bus  System 


Generatorj 


This  system  gives  great  flexibility  of  operation  with  minimum  cost  and  is  suitable 
for  medium-sized  plants.  Dependence  is  placed  on  single  circuit-breakers.  The  station 
may  be  operated  in  separate  independent  halves,  local  feeders  being  fed  from  either  half. 


In  any  switchboard  installation  many  refinements  in  methods 
and  in  apparatus  for  switching  and  measuring  energy  may  be  made, 
and  many  safeguards  against  possible  troubles  may  be  installed. 
Many  of  these  are  justified  because  of  their  convenience  and  the  time 
and  trouble  they  save  the  operator.  Each,  however,  adds  to  the 
complication  of  the  equipment,  and  it  should  be  remembered  that 
usually  the  simplest  scheme  which  will  accomplish  the  purpose  is 
safest  and  most  reliable,  and  represents  the  best  engineering. 


16 


Switchboards  For  Power  Stations 


1541 


The  disposition  to  be  made  of  the  electrical  output  materially 
influences  the  choice  of  instruments  and  meters.  It  also  determines 
to  what  extent  the  service  should  be  guarded  against  failure.  A 
small  station,  for  example,  which  is  maintained  by  an  industrial  plant 
and  whose  entire  output  is  used  in  the  manufacturing  process,  sel- 
dom requires  more  than  enough  instruments  to  secure  safe  operation. 
An  ammeter  for  each  generator  circuit  and  a volt  meter,  which  may 
be  connected  to  any  generator  circuit  by  means  of  receptacles  and 
plug,  with  a second  voltmeter  for  permanent  connection  to  the 
bus-bars,  are  commonly  used.  Non-automatic  oil  switches  may  be 


Outgoing  Lines 


Fig.  10 — Single  High  Tension  Bus  Scheme 

The  generator  and  transformer  are  treated  as  a unit,  and  all  low  tension  switching 
is  thereby  omitted.  The  station  auxiliaries  are  fed  from  any  generator  or  transformer 
circuit  by  means  of  the  auxiliary  bus.  Scheme  used  by  the  Homestake  Mining  Company. 


used  throughout,  with  enclosed  fuses  for  feeder  protection.  An 
occasional  shutdown  of  one  or  more  of  the  circuits  for  a few  minutes 
to  replace  blown  fuses  or  made  quick  repairs,  would  not  be  seriously 
objectionable  in  this  type  of  plant.  One  totalizing  watthour  meter 
will  give  a satisfactory  check  on  the  station  output. 

Where  the  product  of  the  plant  is  of  such  a nature  that  a con- 
stant source  of  power  is  essential,  circuit-breakers  are  usually  employ- 
ed instead  of  fuses.  A double-throw  system  may  be  necessary 
so  that  the  load  can  be  transferred  quickly  to  a clear  bus-bar  in  case 
of  trouble.  The  manufactured  product  may  be  susceptible  to  injury 


1541 


Switchboards  For  Power  Stations 


17 


by  over  or  under  speed  of  the  driving  motors,  thus  requiring  over- 
voltage or  under-voltage  trip  features  on  the  circuit-breakers. 

When  the  output  is  used  to  furnish  light  as  a public  utility,  the 
service  should  be  continuous  and  the  voltage  constant.  The  better 
class  of  apparatus  must  be  used  throughout  on  such  installations, 
a voltage  regulator  employed  and  watthour  meters  installed  on  the 
circuits  where  records  are  desired. 


Outgoing’  Lines 


Dis.  Sw 

Lightning  Arresters 


i i A — I — I — TT — r 


Feeder  Cir*  Br, 
Dis.  Sw. 


XO-- ♦ -o 

0—1 — O 0—1 — o 


X 

0—1—0 


o 1 o O t O O- » O O t -O  0*0  O— j— o 

© © © © © © 


Dis.  Siv. 
Cir,Br. 


Dis.  S\v. 


Trans. 


Dis.  Sw. 


Gin  Br. 


Dis.  Sw 
Cir.  Br, 


Dis.  Sw. 


Generators 


Fig.  11 — Double  Bus,  Double  Circuit  Breaker  System  Throughout 


This  arrangement  permits  the  use  of  any  or  all  of  the  generators,  without  regard  to 
which  of  the  transformers  may  be  in  operation.  It  is  particularly  suitable  where  the 
station  output  is  taken  over  but  two  or  three  transmission  lines  to  the  same  destination. 
This  is  the  arrangement  used  by  the  United  States  Reclamation  Service  in  the  Salt  River 
Project.  Low-tension  connection  similar  to  those  shown  are  used  by  the  Indiana  Steel 
Company  which,  however,  employs  the  single  circuit-breaker  scheme  for  all  high-tension 
systems.  Similar  connections  are  also  used  for  the  Seattle  Light  & Power  Company. 


It  is  clearly  impossible  to  give  definite  rules  as  to.  what  indi- 
cating and  recording  apparatus  should  be  used  and  what  to  omit. 
Each  installation  usually  has  certain  features  requiring  arrange- 
ments more  or  less  special  to  itself.  One  may  require  a watthour 
meter  for  each  generator,  so  that  the  output  of  each  machine  may  be 
checked  and  so  that,  on  light  station  loads  when  but  one  generator  i > 


18 


Switchboards  For  Power  Stations 


1541 


required,  the  watthour  meter  measuring  the  station  output  will  still 
be  working  at  maximum  accuracy.  The  daily  load  curve  may  indi- 
cate that  the  output  is  fairly  constant  over  a continuous  period.  A 
totalizing  watthour  meter  may  then  be  used  to  advantage.  If  the 
feeders  supply  different  sections  of  a factory  or  different  factories, 
or  separate  communities,  a watthour  meter  should  be  used  for  each. 

The  class  of  attendants  in  charge  of  the  switchboard  deter- 
mines, to  a very  great  degree,  how  many  and  what  kind  and  class  of 


Outgoing  Lines  Outgoing  Lines  Outgoing  Line? 


Low-tension  disconnecting  switches  permit  the  connection  of  a generator  direct  to  a 
transformer  (with  or  without  connection  to  bus-bar),  connection  of  generator  to  bus-bar 
with  transformer  dead  or  connection  of  transformer  to  bus-bar  with  generator  dead. 
This  scheme  is  similar  to  that  used  at  the  Post  Falls  Station  of  the  Washington  Water 
Power  Company,  2300-66000  volts.  A generator,  transformer,  or  feeder  may  be  taken  out 
of  service  for  the  examination  or  repair  of  its  circuit-breaker.  All  apparatus  may  be  in 
service  while  the  load  is  removed  from  either  section  of  either  bus-bar  for  repairs  or 
additions. 


instruments  should  be  selected.  Instruments  which  are  not  used, 
and  which  are  not  kept  in  calibration,  are  often  worse  than  none  at 
all,  as  they  only  take  up  valuable  space,  confuse  the  operator  and 
complicate  the  wiring.  The  more  simple  the  equipment  throughout 
an  installation  the  better  the  results  obtained.  It  should  be  the 
engineer’s  rule,  for  stations  of  this  class,  not  to  use  apparatus  in  con- 
nection with  the  switchboard  which  is  not  actually  necessary  to  the 


1541 


Switchboards  For  Power  Stations 


19 


safe  operation  of  the  station.  On  the  other  hand,  this  rule  does  not 
hold  for  the  larger  stations,  whose  operation  is  entrusted  to  trained 
engineers,  for  they  usually  justify  the  use  of  many  of  the  finer  instru- 
ments by  producing  and  maintaining,  with  such  an  equipment,  a 
highly  efficient  power  station. 

As  a guide  to  the  selection  of  a suitable  equipment  the  following 
panel  schedules  are  presented : 


Outgoing  Lines  Outgoing  Lines 


Fig.  13 — Single  Low-Tension  Transfer  Bus,  Double  High-Tension  Bus 

With  this  scheme,  used  by  the  Rio  Janeiro  Tramways,  Light  & Power  Company,  the 
station  may  be  operated  in  four  separate  parts,  if  desired,  any  or  all  of  which  may  be 
connected  together  at  will.  The  double-throw  high-tension  disconnecting  switches 
prevent  interconnecting  the  high-tension  bus-bars  except  by  means  of  the  tie  breakers. 
The  low-tension  connections  make  it  possible  to  connect  a generator  directly  to  its  trans- 
former or  to  any  other  transformer  through  the  transfer  bus. 


Alternating-Current  Generator  Panel 

One  alternating-current  ammeter  (where  phases  are  likely  to  be  unbalanced  an 
ammeter  is  often  supplied  for  each  phase,  or  current  transformers  and  amme- 
ter switch  provided  for  connecting  the  single  ammeter  to  any  phase). 

One  alternating-current  voltmeter  (or  a voltmeter  receptacle  and  plug  to  connect 
to  station  voltmeter). 


20 


Switchboards  For  Power  Stations 


1541 


One  direct-current  ammeter — for  alternating-current  generator  field  (optional)  ‘ 
One  indicating  wattmeter  (optional). 

One  power  factor  meter  (optional). 

One  frequency  meter  (optional). 

One  ground  detector  (optional;  one  ground  detector  is  usually  connected  to  each 
set  of  main  bus-bars  where  there  are  two  or  more  generators). 

One  field  discharge  switch. 

One  controller  for  engine  or  waterwheel  governor  (optional  and  only  supplied  when; 

engine  governor  is  controlled  at  the  switchboard  in  synchronizing). 

One  rheostat  for  generator  field  (usually  supplied  with  generator). 

One  rheostat  for  exciter  field — required  only  when  generator  has  its  own  separate 
exciter  (usually  supplied  with  exciter). 

One  synchronizing  outfit  (not  required  if  but  one  generator  is  to  be  installed 
which  is  not  to  operate  in  parallel  with  an  outside  source  of  power). 

One  non-automatic  switch  or  circuit-breaker  for  main  circuit. 

Necessary  current  and  potential  transformers. 

Discussion 

Field  ammeters  are  considered  almost  indispensable  by  most 
operators,  as  they  assist  in  properly  adjusting  the  field  so  that  the 
machine  will  take  its  load.  All  generators  are  more  efficient  with  the 
field  adjusted  to  a certain  value,  as  determined  by  their  design. 
The  field  ammeters  enable  the  operator  to  make  this  adjustment 
accurately  at  all  times.  They  indicate  the  presence  of  cross-currents 
between  machines,  and  also  assist  materially  in  locating  any  trouble 
which  may  occur  at  the  generator.  Machines  operating  in  parallel 
should  have  either  field  ammeters  or  indicating  wattmeters,  preferably 
both,  for  indicating  proper  operating  conditions. 

Indicating  wattmeters  while  directly  indicating  the  output  of 
each  machine  will  show  what  portion  of  the  load  is  carried  by  each 
generator.  This  cannot  be  determined  by  means  of  the  ammeters 
and  voltmeters  alone,  as  they  do  not  take  into  account  the  power- 
factor  of  the  circuit. 

Power  factor  meters  also  indicate,  but  in  a different  manner, 
how  the  generators  are  dividing  the  load.  In  combination  with  the 
ammeters  and  voltmeters  they  will  permit  the  ready  calculation  of 
the  load  in  watts.  They  also  guide  the  attendant  in  adjusting  the 
field  excitation  to  obtain  the  best  results.  Power  factor  meters  are 
sometimes  used  in  place  of  indicating  wattmeters. 

Voltage  readings  for  the  generators  are  usually  taken  by  means 
of  the  “machine”  voltmeter,  which  is  usually  mounted  on  a swinging 
bracket  at  the  end  of  the  board,  and  the  voltmeter  receptacles  on  the 
individual  panels.  Most  operators  require  a second  voltmeter 
mounted  on  the  same  bracket  with  the  machine  voltmeter  and  con- 
nected permanently  to  the  bus-bar.  This  arrangement  permits  a 


1541 


Switchboards  For  Power  Stations 


21 


simultaneous  comparison  of  the  bus-bar  and  machine  voltages  when 
synchronizing. 

The  synchronizing  outfit  may  consist  of  synchronizing  recep- 
tacles with  lamps,  or  with  synchroscope,  or  both.  The  most  popular 
practice  is  to  place  the  synchroscope  with  two  synchronizing  lamps 
on  a swinging  bracket  beneath  the  two  voltmeters,  where  the  entire 
combination  may  be  seen  at  a glance  while  synchronizing. 

Frequency  meters  are  an  aid  in  synchronizing,  as  they  indicate 
the  speed  of  the  generator.  They  are  often  used  as  one  of  the  indi- 

Feedcrs  Feeders 


mu  mu  mu  mu 


Fig.  14 — Sectionalized  Generator  and  Main  Feeder  Bus  System  With  Group 
Feeder  Bus 

By  this  system  great  flexibility  may  be  obtained  for  large  stations  feeding  a thickly 
settled  community  at  generator  voltage.  The  station  may  be  operated  in  halves  or  any 
feeder  or  group  of  feeders  may  be  served  from  either  half.  Similar  connections  are  used 
by  the  Cleveland  Electric  Illuminating  Company. 


vidual  panel  instruments  with  large  generators,  but  otherwise  but 
one  station  frequency  meter  is  supplied.  Where  there  are  two  or 
more  sets  of  bus-bars,  or  several  stations  feeding  into  a common 
transmission  line  their  use  is  often  of  vital  importance. 

Watthour  meters  are  not  commonly  placed  on  generator  panels. 
They  are  usually  applied  to  the  feeder  circuits,  but  a load  totalizing 
watthour  meter  is  also  often  employed  when  it  can  be  conveniently 
applied.  They  are,  however,  sometimes  used  to  record  the  output 
of  the  individual  generators. 

Relays  are  seldom  used  with  generator  circuits  except  to  pro- 
tect against  reverse  power,  which  would  motor  the  unit  and  per- 


22 


Switchboards  For  Power  Stations 


1541 


haps  injure  the  prime  mover.  Sometimes,  however,  overload  relays 
are  used  to  indicate  excessive  load  by  operating  a signal.  Under- 
load relays  may  be  used  in  a similar  manner. 


»4>~n 

I 


Lightning: 

^ V^Coil!  2.  Arrester 


rh  rU 


rU. 


rh, 


Dis.  Sw. 
Oil  Cir.  E 
Dis.  Sw. 


Fig.  15 — Single  Sectionalized  Low-Tension  Bus,  With  Two  High-Tension  Buses, 

One  of  Which  Is  Sectionalized 

The  station  may  be  operated  as  four  complete  units  (generator,  transformer,  and 
line  separate),  or  any  generator  may  feed  any  bank  of  transformers  through  the  low-ten  - 
sion  bus-bar.  The  step-down  transformer  for  local  or  station  service  permits  the  low- 
tension  bus-bar  and  circuit-breakers  to  be  taken  out  of  service  entirely  without  inter- 
fering with  the  load.  This  scheme  is  used  by  the  Washington  Power  Company,  Little 
Falls  Station. 


Feeder  Panels  for  Motor  or  Power  Service 

One  alternating-current  ammeter  (ammeter  switch  or  one  ammeter  per  phase  may 
be  used  if  phases  are  unbalanced). 

One  watthour  meter  (optional). 

One  automatic  overload  circuit-breaker. 

One  relay  (optional). 

Necessary  current  and  potential  transformers. 

Discussion 

Unless  it  is  desired  to  have  the  circuit-breaker  trip  instantane- 
ously at  a certain  predetermined  overload,  an  inverse  time  limit  or 
definite  time-limit  relay  should  be  applied.  Many  elect rically-oper- 


1541 


Switchboards  For  Power  Stations 


23 


ated  circuit-breakers,  especially  of  the  higher  capacities,  require 
some  form  of  relay  to  render  them  automatic. 

Load  Panel 

Any  or  all  of  the  following  instruments  may  be  placed  on  the 
load  panel,  and  most  of  them  can  be  obtained  in  the  graphic  record- 
ing type  if  desired : — Watthour  meter,  voltmeter,  ammeter,  indicat- 
ing wattmeter,  frequency  meter,  synchroscope,  power  factor  meter, 
or  static  ground  detector.  Sometimes  the  generator  voltage  regula- 
tor, when  used,  is  placed  on  the  load  panel,  especially  when  there  is 
sufficient  space  available  which  would  otherwise  be  vacant. 


utum  iuum  mum 


Fi^.  16 — Single  Bus  Feeder  Group  System 


This  arrangement  is  suitable  for  stations  employing  large  units,  each  supplying 
a number  of  feeders.  Each  unit  and  its  group  of  feeders  may  be  operated  independently 
or  all  may  be  operated  from  one  main  bus.  This  arrangement  is  used  by  the  Common- 
wealth Edison  Company,  Chicago,  at  its  Quarry  Street  Station. 


Synchronous  Motor  Panel 

One  alternating-current  ammeter. 

One  direct-current  field  ammeter. 

One  indicating  wattmeter  (optional). 

One  power  factor  meter  (optional). 

One  field  rheostat  (usually  supplied  with  motor). 

One  field  discharge  switch  (may  be  omitted  when  motor  has  a direct-connected 
exciter). 

One  synchronizing  outfit  (not  required  if  motor  is  self-starting). 

One  automatic  overload  oil  circuit-breaker. 

One  relay  (optional). 

Necessary  current  and  potential  transformers. 


24 


Switchboards  For  Power  Stations 


1541 


Discussion 

But  one  ammeter  will  be  required  for  this  panel,  as  there  should 
be  the  same  current  in  each  phase.  The  field  ammeter  is  of  great 
assistance  in  making  a proper  adjustment  of  the  field  to  meet  the 
desired  conditions.  Its  importance  is  further  increased  by  the  fact 
that  motor  guarantees  are  usually  based  on  a certain  definite  field 
current.  .The  indicating  wattmeter  or  power  factor  meter,  as  in 
the  case  of  the  generator,  will  assist  the  operator  to  adjust  the  field 
properly  so  that  the  motor  will  take  its  proper  load.  An  indicating 


1 J j i j 1 i 


By  this  system  all  groups  may  be  operated  either  independently  or  in  parallel.  The 
large  transformers  may  have  the  capacity  of  two  or  more  generators.  A number  of  dupli- 
cate lines  of  different  characteristics  may  be  taken  from  the  same  power  station.  This  is 
the  arrangement  used  by  the  Mt.  Hood  Railway  & Power  Company. 


wattmeter  when  connected  properly  by  means  of  a suitable  switching 
device  to  its  transformers  will  read  true  watts  with  the  switch  thrown 
one  way  and  the  wattless  volt-amperes  when  thrown  the  other  way. 

The  field  switch  is  made  double  throw  for  machines  which  start 
as  induction  motors  to  permit  short-circuiting  the  field  during  start- 
ing. The  same  machine,  however,  when  equipped  with  a direct- 
connected  exciter  need  not  be  provided  with  a field  switch,  as  the 
field  is  short-circuited  across  the  exciter  armature  when  the  field 
switch  is  closed.  If  a field  switch  is  provided  it  may  be  single  throw. 


1541 


Sivitch boards  For  Power  Stations 


25 


When  the  motor  is  not  self-starting  the  usual  single-throw 
circuit-breaker  may  be  used.  When  it  is  started  from  taps  on  its 
own  power  transformers  a double-throw  circuit-breaker,  automatic 
on  the  running  side  only,  is  used.  When  auto-transformers  are 
employed  for  starting,  a special  double-throw  auto-starter  switch, 
automatic  only  on  the  running  side  and  with  provision  for  discon- 
necting the  auto- transformers  from  the  source  of  power,  is  used. 

For  very  large  motors,  and  for  motors  connected  close  to  large 
generating  stations,  three  interlocked  circuit-breakers  are  usually 
employed ; one  automatic,  for  connecting  the  machine  to  the  source 
of  power,  one  for  starting,  and  one  for  disconnecting  the  auto-trans- 
formers. 

Line  Panels 

For  Transmission  Lines  to  Sub-Stations  or  Tie  Lines  to  Other  Power  Stations. 
One  ammeter  per  phase  (or  one  ammeter  with  polyphase  switching  device). 

One  indicating  wattmeter  (optional). 

One  power  factor  meter  (optional),  or 
One  reactive  factor  meter  (optional). 

One  voltmeter,  or  voltmeter  receptacle  (optional). 

One  watthour  meter  (optional). 

One  synchronizing  outfit  (required  only  for  tie  line). 

One  automatic  circuit-breaker. 

One  relay  (optional). 

Necessary  current  and  potential  transformers. 

Discussion 

Three  ammeters  are  usually  considered  necessary,  particularly 
for  overhead  lines,  as  they  not  only  give  a direct  indication  of  unbal- 
ancing of  the  load,  but  also  of  any  trouble  which  may  occur  on  any 
phase. 

Power-factor  meters  are  very  commonly  used  on  these  panels 
as  an  efficient  system  should  operate  at  high  power  factor,  and  the 
instruments  will  indicate  those  parts  of  the  system  which  require 
modifications  of  their  load  to  better  the  power  factor  which  in  turn 
reduces  unnecessary  line  losses. 

Voltmeters  may  be  compensated  to  read  the  voltage  obtaining 
at  the  end  of,  or  at  some  point  along  the  transmission  line.  For  tie 
lines  the  voltmeter  is  useful  in  synchronizing  with  other  stations. 
The  voltmeter  receptacle  may  be  used  instead,  to  read  the  potential 
by  means  of  one  of  the  station  voltmeters. 

Where  power  may  be  taken  over  the  line  in  either  direction  the 
indicating  wattmeter  should  be  double  reading  and  two  watthour 
meters  provided,  connected  to  record  power  in  opposite  directions, 
and  so  arranged  that  the  mechanism  will  not  reverse. 


26 


Switchboards  For  Power  Stations 


1541 


Alternating-Current  Rotary  Converter  Panel 

One  alternating-current  ammeter. 

One  reactive  factor  meter,  or 
One  power  factor  meter  (optional). 

One  main  automatic  inverse-time-limit  overload  oil  circuit-breaker  (for  high- 
tension  side  of  transformers).  (Equipped  with  low-voltage  release  and  an 
auxiliary  switch,  for  tripping  breaker  on  direct-current  side  of  converter). 
One  single-throw  knife  switch,  for  synchronizing  resistance  (required  only  for 
converters  started  by  an  alternating-current  motor  using  the  method  requiring 
synchronizing). 

One  synchronizing  outfit  (not  required  when  rotary  is  self-starting  from  trans- 
former taps  or  by  means  of  the  self-synchronizing  alternating-current  motor 
starting  method). 

One  single-throw  switch  for  starting  motor  when  used. 

One  set  knife  switches  (for  low-tension  side  of  transformers  when  rotary  is  self- 
starting. Usually  mounted  on  separate  starting  panel  when  rotary  is  over 
500  kilowatt  capacity). 

One  set  of  single-throw  knife  switches  (required  in  main  low-tension  leads  for 
motor-started  converters  whose  motors  connect  to  the  converter  transformers) 
Necessary  current  and  voltage  transformers. 

Discussion 

Rotary  converters  are  designed  to  operate  most  satisfactorily  at 
a certain  definite  power  factor,  usually  unity,  and  it  is  therefore 
almost  necessary  that  either  a reactive  factor  meter  or  a power  factor 
meter  be  used. 

In  operating  a shunt-wound  converter  it  is  very  desirable  that 
the  reactive  factor  be  zero  (100  per  cent  power  factor).  With  com- 
pound-wound converters  it  is  the  practice,  for  average  conditions, 
to  operate  the  converter  with  shunt  field  adjusted  to  give  a slightly 
lagging  current  in  the  armature  at  light  loads.  With  increase  of 
direct-current  load  the  field  strength  increases  to  produce  a leading 
current  at  full  load  and  overloads,  and  thereby  obtain  the  desired 
compounding  effect. 

Reactive  factor  meters  are  preferable  to  power  factor  meters  for 
indicating  proper  converter  operating  conditions  as  they  give  a more 
impressive  and  nearly  direct  indication  of  the  amount  of  wattless 
current;  for  example  a variation  in  power  factor  from  unity  of  2 per 
cent  corresponds  to  19.7  per  cent  reactive  factor. 

It  is  important  in  this  connection,  however,  that  the  reactive 
factor  meter  indicate  the  reactive  factor  of  the  rotary,  and  not  of  the 
combination  of  rotary  and  transformer  bank.  To  insure  this  the 
meter  should  be  connected  to  transformers  on  the  secondary  leads  of 
the  power  transformers  or,  if  connected  on  the  primary  side  of  the 
meter,  should  be  calibrated  to  read  the  correct  reactive  factor  at  the 


1541 


Switchboards  For  Power  Stations 


27 


value  at  which  the  rotary  should  normally  operate,  and  should  be 
provided  with  a calibration  curve  to  enable  correct  readings  to  be 
made  at  other  points  on  the  scale.  The  proper  choice  of  switching 
apparatus  for  converters  depends  on  the  scheme  of  operation,  the 
size  of  the  rotary,  the  characteristics  of  the  power  supply  and  the 
nature  of  the  load.  Its  combinations  are  so  many  that  space  does 
not  permit  of  a complete  discussion. 

Direct- Current  Exciter  Panel 

One  direct-current  ammeter. 

One  voltmeter  (or  receptacle  to  connect  to  main  direct-current  voltmeter). 

One  single-pole  non-automatic  circuit-breaker  (optional). 

One  rheostat  (usually  supplied  with  exciter). 

One  three-pole  main  switch  (two-pole  if  for  operating  singly  or  if  shunt  wound) 
or  separate  single-pole  switches. 

Two  exciters  may  be  controlled  from  one  “double  exciter  panel’  ’ by  adding  to  the 
above  schedule  one  ammeter,  one  rheostat,  voltmeter  receptacle,  and  the 
necessary  main  switch. 

Comparative  Space  Required 

The  self-contained  switchboard  (Class  1)  occupies  less  space 
than  any  other.  Its  floor  plan  takes  the  shape  of  a long,  narrow  rect- 
angle, however,  which  sometimes  involves  more  valuable  space 
than  the  shorter  boards  of  Classes  2 and  3,  whose  switching  devices, 
transformers,  and  buses  may  be  mounted  at  a distance  from  the 
panel  in  a less  important  and  probably  more  favorable  location. 
Frequently  it  is  found  that  owing  to  the  disposition  of  the  space 
available  for  switching  equipment  a board  of  Class  2 or  3 must 
be  used,  although  otherwise  a Class  1 board  would  have  answered. 

Figs.  1,  2 and  3 give  an  idea  of  how  the  same  equipment  com- 
pares in  space  occupied  when  designed  according  to  the  three  classi- 
fications given  herein.  Fig.  3 has  little  or  no  advantage  over  Fig. 
2 in  space  occupied,  but  has  the  advantage  that  the  two  parts  of 
Fig.  2,  that  is,  the  panels  and  switching  devices,  must  be  within  the 
range  of  mechanical  operation  by  means  of  bell-cranks  and  connect- 
ing rods,  while  the  two  parts  of  Fig.  3 are,  comparatively,  unlimited 
as  to  location. 

Comparative  Cost 

The  cost  of  the  self-contained  board  is  usually  less  than  that  of 
any  other  type.  The  remote-control  mechanically-operated  board, 
with  switching  devices  and  bus-bars  arranged  for  wall  mounting, 
may  be  made  as  cheap,  and  sometimes  even  cheaper,  as  the  saving 
in  length  of  board  may  neutralize  the  additional  cost  of  operating 


28 


Switchboards  For  Power  Stations 


1541 


mechanism.  Assuming  the  cost  of  the  switchboard  shown  in  Fig.  1 
to  be  100  per  cent,  the  cost  of  the  same  equipment  in  Fig.  2 would 
be  approximately  115  per  cent,  and  for  Fig.  3 would  be  140  per  cent. 

In  some  cases  great  saving  in  main  cables  can  be  effected  by 
arrangements  possible  with  Class  2 and  3 boards,  which  may  result 
in  reducing  the  total  price  of  the  installation  to  the  same  figure,  or 
even  less  than  if  the  self-contained  switchboard  were  used. 


1541 


Switchboards  For  Power  Stations 


29 


II 

SELF  - CONTAINED  SWITCHBOARDS  OF  6600 
VOLTS  OR  LESS  WITH  OIL  CIRCUIT-BREAK- 
ERS AND  BUS-BARS  SUPPORTED  FROM 
THE  BACK  OF  THE  PANELS 

By  C.  H.  SANDERSON 

The  most  common  generating  voltages  used  for  alternating- 
current  power  stations  of  moderate  capacity  for  the  usual  classes 
of  electric  service  are  2200  and  6600  volts.  The  term  “moderate 
capacity,”  whem  applied  either  to  a generating  station  or  to  a single 
generating  unit,  conveys  a very  different  meaning  now  than  it  did 
a few  years  ago.  Our  moderate  capacities  of  today  were  then  maxi- 
mum capacities,  but  the  switchboard  problems  were  even  more  serious 
ones  than  those  which  confront  the  engineer  today.  They  were  then 
venturing  into  new  and  untried  fields,  while  now  the  results  of  their 
pioneering  are  being  perfected.  Twenty  years  ago  the  self-contained 
switchboard  had  the  entire  field  to  itself,  as  there  was  then  no  neces- 


Fig.  1 — Single  Bus-Bar  System 

Generators  and  feeders  at  opposite  ends  of  bus-bars  permitting  use  of  totalizing 
instrument  transformers. 


sity  for  any  other  class.  With  the  advent  of  2200  and  6600- volt  gen- 
erators and  transformers  came  many  different  types  of  high-voltage 
airbreak  switches,  circuit-breakers,  and  plug  receptacles,  most  of 
which  were  expensive,  untrustworthy  and  even  dangerous  when  com- 
pared with  the  oil-insulated  devices  which  have  replaced  them. 

Application 

Experience  has  shown  that  for  the  usual  conditions  of  service 
this  class  of  switchboard  should  not  be  applied  to  stations  whose 
capacity  exceeds  '""SOOb  k.v.a.,  three  phase.  Moreover,  it  is  not  con- 
sidered good  practice  to  exceed  6600  volts,  and  it  is  usually  advisable 

*70  per  cent  of  this  for  single-phase;  140  per  cent  for  two-phase. 


30 


Switchboards  For  Power  Stations 


1541 


to  confine  its  application  to  2500  volts  or  less.  The  reason  for  this 
limitation  lies  in  the  danger  to  attendants  from  high-voltage  appa- 
ratus when  in  close  proximity  to  low  voltage  control  and  instrument 
wiring,  rheostats,  etc.,  which  require  inspection  and  occasional  re- 
pairs. Also  in  the  necessity,  with  the  higher  voltages,  of  longer  and 
higher  switchboards  to  gain  sufficient  spacing  distances.  It  is  rec- 
ommended that  the  size  of  individual  circuit-breakers  and  switches 
for  this  type  of  switchboard  be  limited  to  800  amperes  or  less  per  pole 
at  2500  volts  on  account  of — 

a — The  advisability  of  limiting  the  amount  of  power  handled  by  one  circuit- 
breaker  mounted  directly  on  the  panel. 

b — Difficulty  of  obtaining  adequate  insulation  distances  between  the  heavy 
bus-bars  and  connections  required  for  larger  capacities. 

c — The  mechanical  strains  imposed  upon  the  panels  by  the  larger  capacity 
circuit-breakers  with  their  heavy  connections,  due  both  to  their  dead  weight 
and  to  the  shock  of  operation. 


Tot.  Cur.  Trans  Tot.  Cur.  Trans.  Tot.  Cur.  Trans. 


Generators  Feeders  Feeders  Generators 

Fig.  2 — Single  Sectionalized  Bus-Bar  System 
Station  may  be  operated  in  halves  or  as  a unit  as  the  load  requires. 


There  may  be  conditions  in  certain  installations  where  it  is 
advisable  to  exceed  these  limits.  No  hard  and  fast  rule  can  be  made, 
as  few  installations  are  governed  by  the  same  conditions.  The  fol- 
lowing suggestions,  although . applying  to  all  boards  of  this  class, 
should  particularly  be  followed  when  the  ultimate  capacity  con- 
nected to  the  bus-bars  will  be  greater  than  the  recommended  limit: 

The  first  consideration  is  the  circuit-breaker.  The  type  chosen  should  be 
of  rugged  design  which  will  carry  its  rated  current  continuously  with  not  more 
than  30  degrees  C.  rise  in  temperature  on  conducting  parts  and  which  will  not 
permit  the  escape  of  oil,  either  through  leaking,  creeping  or  expulsive  effect  of 
short-circuits.  It  should  have  a breaking  capacity  sufficient  to  rupture,  in  case 
of  a short  circuit,  the  current  sustained  after  the  interval  between  the  first  rush 
of  current  and  the  instant  at  which  the  breaker  is  set  to  open. 

If  rubber-covered  wire  is  used  for  bus-bars  or  connections,  it  should  be 
covered  with  a flame-proof  braid.  The  panels  should  be  of  sufficient  width 
that  there  will  be  ample  space  between  adjacent  circuit-breakers  in  which  to 
take  away  their  leads.  Instrument  transformers  should  preferably  be  mounted 


1541 


Switchboards  For  Power  Stations 


31 


apart  from  panels,  but  when  located  on  rear  of  switchboard  should  be  rigidly 
secured  to  strong  brackets  to  prevent  vibrations  due  to  heavy  overloads  or  short- 
circuits. 

The  bus-bars  should  be  as  far  apart  as  the  design  will  conveniently  permit 
and  should  be  located  near  the  top  of  the  board.  This  arrangement  places  them 
out  of  reach  of  the  attendants,  at  the  same  time  giving  accessibility  to  the  back 
of  the  board,  and  also  removes  them  from  the  immediate  vicinity  of  the  circuit- 
breakers. 

Special  precautions  should  be  taken  to  insure  that  nothing  can  fall  across 
the  bus-bars  or  connections.  Bus-bar  screens  or  suitable  insulation  or  both  should 
be  used.  Insulation  without  screens  is  perhaps  sufficient  for  bus-bars  of  small 
cross-section,  but  heavy  capacity  bus-bars  require  ventilation  and  for  them  this 
arrangement  should  be  reversed. 

Moving  parts  such  as  rheostat  chains,  mechanical  connecting  rods,  etc., 
should  be  so  arranged  that  their  failure  will  not  entangle  other  apparatus  or 
cause  short-circuits.  They  should  be  run  in  pipes  or  protected  by  shields  where 
necessary. 

Tot.  Cur.  Trans. 


Generator  and  feeders  at  opposite  ends  of  bus-bars  permitting  use  of  totalizing 
instrument  transformers. 

Choice  of  System 

The  principal  factors  influencing  the  choice  of  the  system  are — 
the  nature  of  the  service  to  be  supplied,  the  size  and  number  of  the 
units  to  be  employed,  and  the  expense  justifiable  to  give  continuity 
of  service.  Other  factors,  such  as  a diversity  of  apparatus  to  be 
controlled  or  the  sequence  of  purchase,  may  have  considerable 
influence  in  the  choice  and  also  in  the  growth  of  the  system.  Sim- 
plicity should  be  the  principal  aim.  The  simplest  system  which 
will  do  the  work  satisfactorily  naturally  represents  the  best  engi- 
neering. 

First  and  most  usual  is  the  single-throw  system.  Fig.  1.  It 
is  the  least  expensive  as  regards  first  cost,  installation,  and  main- 
tenance, and  lends  itself  readily  to  later  additions  or  modifications. 
It  is  used  in  all  cases  except  where  special  requirements  of  the  ser- 
vice or  added  precautions  against  failure  of  supply  require  modifica- 
tions, such  as  in  Fig.  2,  or  the  adoption  of  the  double-throw  system, 


32 


Switchboards  For  Power  Stations 


1541 


Fig.  3.  The  single-throw  bus  with  tie  circuit-breaker,  Fig.  2,  per- 
mits operation  of  a station  in  separate  halves,  which  is  particularly 
desirable  where,  for  example,  the  left  half  of  the  bus  may  feed  a 
railway,  or  other  power  load,  while  the  right  half  feeds  a lighting 
load.  During  the  day  while  the  power  is  large  and  the  lighting 
load  is  very  small,  the  tie  breaker  is  closed.  When  the  lighting 
load  comes  on,  the  tie  is  opened;  and,  if  later  in  the  evening  the 
power  load  disappears  altogether,  or  its  fluctuations  are  unobjec- 


Fig.  4 — Smallest  Type  of  Self-Contained  Switchboard. 

Controlling  two  alternating-current  generators  with  their  exciters  and  two  fused 
feeder  circuits  with  totalizing  watthour  meter. 


tionable,  the  tie  breaker  may  again  be  closed.  The  same  procedure 
is  possible  where  the  double  bus.  Fig.  3,  is  employed.  This  system, 
though  more  complicated,  more  expensive,  and  retiuiring  more 
space,  gives  great  flexibility  in  the  handling  of  load.  Moreover, 
the  double  bus  ordinarily  gives  adeciuate  assurance  of  continuity 
of  service,  and  permits  of  examination  and  repairs  of  any  circuit- 
breaker  of  connections  thereto,  or  to  either  bus,  without  discontinu- 
ing any  part  of  the  service. 


1541 


Switchboards  For  Poiuer  Stations 


33 


Choice  of  Apparatus 

Standard  panels  containing  standard  apparatus  for  various 
classes  of  service  are  listed  by  the  larger  electrical  manufacturing 
companies.  Three  distinct  types  are  commonly  provided  for  as 
follows: 

1 — The  small  plant  where  the  most  inexpensive  board  is  desired,  with  only 
sufficient  apparatus  to  fill  the  absolute  requirements  for  operation  of  the  plant, 
as  in  Fig.  4. 


Fig.  5 — Medium-Size  Self-Contained  Switchboard  for  Furnishing  Light  and  Power  for 

Small  Town 

Controls  two  alternating-current  generators,  with  Tirrill  regulator  voltage  control, 
two  exciters,  two  power  feeders,  rectifier  circuits  for  arc  lights  and  alternating-current 
end  of  synchronous  motor-generator  set  for  supplying  direct-current. 

2 —  For  plants  of  medium  capacity  larger  switchboards  are  advisable,  wherein 
the  circuits  are  more  carefully  protected  but  provided  with  few  meters,  as  in  Figs. 
5,  7,  8,  and  9. 

3 —  For  the  larger  plants  where  the  best  of  circuit-breakers  are  required 
and  where  a full  complement  of  instruments  is  necessary,  as  in  Fig.  10, 

The  choice  of  apparatus,  and  therefore  the  design  of  the  switch- 
board, depends  on  the  size  and  disposition  of  the  output.  The 
grade  of  intelligence  of  the  attendants  may  also  have  considerable 


34 


Switchboards  For  Power  Stations 


1541 


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1541 


Switchboards  For  Power  Stations 


35 


influence.  The  magnitude  of  the  output  determines  to  a very  consid- 
erable extent  the  type  of  switching  devices  to  be  used.  The  smaller 
capacity  circuit-breakers  for  2200,  3300  and  4400-volt  service  usually 
have  an  ultimate  breaking  capacity  of  approximately  3000  k.v.a. 


Fig.  7 — Front  and  Rear-View  Drawings  of  Switchboard,  Shown  in  Fig.  5 
Showing  the  details  of  arrangement  and  location  of  apparatus. 


The  type  of  circuit-breaker  chosen  must  be  capable  of  opening  the 
maximum  output  of  the  station.  For  example,  if  the  generating 
units  consist  of  three  800-k.v.a.  machines  of  the  assumed  character- 
istics, the  circuit-breakers  must  have  an  ultimate  breaking  capacity 
of  at  least  2400  k.v.a.  when  set  for  instantaneous  tripping. 


Panel  No.  5 P*nel  No,  4 Panel  No.  3 


36 


Switchboards  For  Power  Stations  1541 


z. 

1 


7m 


bsk: 


€>= 


mt 


o ,« 
1 


J\~< 


Fig.  8 — Detail  Diagram  of  Connections  of  Switchboard  Shown  in  Figs.  5 and  7 

View  from  the  rear  of  board.  All  apparatus  is  shown  as  nearly  as  possible  in  its  relative  location.  A single  line  diagram  of  the  board  is  shown 
in  the  lower  left-hand  corner. 


1541 


Switchboards  For  Power  Stations 


37 


The  selection  of  non-automatic  oil  circuit-breakers  and  oil 
switches  is  not  influenced  in  this  way  by  the  capacity  of  the  station, 
except  as  they  will  be  called  upon  under  extreme  conditions  to  open 
the  circuit.  They  should  never  be  required  to  open  the  circuit  on 
an  overload  or  even  on  a normal  load,  except  where  absolutely  nec- 
essary to  save  some  more  valuable  piece  of  apparatus.  Their  prin- 
cipal function  is  that  of  main  disconnecting  switch.  They  permit 
quicker  and  safer  closing  or  opening  of  the  circuits  than  could 
be  accomplished  by  the  usual  lever-type  disconnecting  switches. 


Fig.  9 — Rear  of  a Medium-Sized  Board 

Showing  main  and  small  wiring  and  bus-bars  in  place.  Absence  of  instrument 
transformers  and  other  details  gives  simple  and  pleasing  appearance. 

They  are,  therefore,  commonly  used  between  generators  and  bus- 
bars, where  automatic  action  is  undesirable,  but  where  quick  manual 
operation  is  necessary,  as  during  synchronizing.  If  it  is  desired 
that  the  non-automatic  breakers  be  suitable  for  clearing  any  abnormal 
condition  which  is  not  taken  care  of  by  the  automatic  breakers,  it  is 
usually  safe  to  assume  that  by  the  time  the  breaker  has  been  opened 
by  hand  the  energy  is  reduced  one-half  its  value  at  the  instant  the 
breaker  would  have  opened  had  it  been  automatic  instantaneous-trip. 


38 


Switchboards  For  Power  Stations 


1541 


If,  however,  the  conditions  are  such  that  the  maximum  current  on 
short-circuit  may  be  sustained  longer  than  the  time  required  to  man- 
ually operate  the  breaker,  the  ultimate  breaking  capacity  should  be 
the  same  for  non-automatic  as  for  instantaneous  operation.  The 
the  principal  limiting  factor  is  the  amount  of  current  which  will  flow 
on  short-circuit. 

The  better  class  of  automatic  circuit-breakers  designed  for 
switchboard  mounting  should  be  capable,  on  instantaneous  opera- 
tion, of  opening  short  circuits  on  generating  systems  of  capacities 


Fig.  10 — Large  Capacity  Switchboard  (Feeders  Not  Shown),  Having  a Full  Complement  of 

Instruments 


The  panels  shown  control  two  exciters,  an  induction  motor  for  one  of  the  exciters, 
voltage  regulator,  two  300-ampere  and  one  600-ampere  alternating-current  three-phase 
generators.  Each  generator  panel  has  three  ammeters,  power  factor  meter,  alter- 
nating-current voltmeter,  indicating  wattmeter  and  field  ammeter. 

from  5000  to  12500k.v.a.  The  high-capacity  circuit-breakers  usually 
have  a separate  tank  for  each  pole,  with  the  trip  coils,  which  are 
actuated  from  current  transformers,  mounted  outside  the  tanks. 
The  cheaper  class  of  circuit-breakers  usually  have  series  trip  coils, 
that  is,  coils  through  which  the  entire  current  of  the  circuit  must 
pass,  and  a single  tank  containing  all  the  poles  and  sometimes  the 
trip  coils. 

Choice  of  Panel  Design 

Dimensions — The  size  of  the  panel  and  the  design  of  the  frame 
should  be  in  keeping  with  the  apparatus  to  be  mounted  thereon 


1541 


Switchboards  For  Power  Stations 


39 


A small  schedule  of  apparatus  of  the  cheaper  type  and  of  small 
capacity  should  have  a small  panel  with  light  framework  to  bal- 
ance the  design  properly.  Obviously  a large  schedule  of  heavy-ca- 
pacity apparatus  would  be  entirely  out  of  place  if  mounted  on 
small  panels  with  light  framework.  Two  distinct  forms  of  panels 
appear  prominently  among  the  many  special  panels  which  have  been 
used ; the  90-inch  panel  with  two  or  more  sections  of  panel  material 
covering  the  entire  frame  from  top  to  floor,  Fig.  6 (1  to  16),  and  the 
76-inch  panel  with  one  section  of  panel  material  48  inches  high  with 
the  frame  extending  uncovered  the  remainder  of  the  distance  to  the 


board  90  Inches  High 

Made  from  standard  3 by  2 by 
Vi  inch  angle-iron  with  corner 
angles  of  the  same  shape,  with 
two wrought-iron straps 
inch  and  with  6-inch  channel 
base  weighing  8 pounds  per  foot. 


90  Inches  High 

Made  from  1 Vi-inch  wrought- 
iron  pipe  with  one  wrought-iron  top 
strap  by  1^  inch  and  with  cast- 
iron  foot  nuts  and  panel  supports. 


floor.  Fig.  6 (17  to  28).  Both  forms  may  be  supported  by  either  angle 
or  tubular  framework,  but  the  latter  form  is  usually  mounted  on 
tubular  frame,  as  the  round  piping  extending  below  the  panel 
section,  with  large  ornamental  foot  nuts,  presents  a more  finished 
appearance. 

Panel  Sections — The  determination  of  the  proper  number  of 
sections  per  panel  may  be  influenced  by  design  and  arrangement  of 
apparatus,  the  appearance,  strength  of  the  material,  and  facility  in 
erecting  and  interchanging.  A wide  range  of  selection  is  presented  by 
the  standard  lines  carried  in  stock  by  the  manufacturers,  and  wherever 
possible  some  standard  size  should  be  chosen.  These  sizes  usually  per- 


40 


Switchboards  For  Power  Stations 


1541 


mit  the  best  arrangement  and  are  the  result  of  years  of  experience. 
Their  choice  will  enable  manufacturers  to  quote  their  minimum  price 
and  delivery.  This  is  even  more  true  when  additions  or  modifications 
to  an  existing  marble  switchboard  are  to  be  made,  for  while  the  large 
stocks  of  polished  marble  carried  by  the  manufacturers  enable  them  to 
match  an  existing  board  closely,  special  sizes  must  be  ordered  direct  f rom 


Inst.  & Svn.  Busses 


Exc. 

Inst.  & Syn,' 
Busses 


I.XC. 


Regulator 
^^^Mai^^usBa^ 


(d) 

ylnst.  & Syn. 
Busses 


Bracket 

Generators 

Feeders 

Generators 

Bracket 

1 

1 ^ 

f ^ 

Fig.  13 — Usual  Arrangement  of  Panels  and  Bus-Bars  System  for  Switchboard  Panels 

In  the  arrangement  shown  at  c the  station  load  consists  of  two  parts,  lighting  and 
power.  A tie  switch  is  provided  to  permit  parallel  operation  of  the  two  halves  of  the 
station  when  desirable.  The  feeder  panels  are  placed  at  the  extreme  ends  of  the  board 
to  permit  addition  to  feeders  without  disturbing  the  rest  of  the  board,  lighting  feeders 
being  taken  out  at  one  end  and  power  feeders  at  the  other.  The  switchboard  and  exciters 
are  located  in  the  center  of  the  station  with  the  alternating-current  generators  symmet- 
rically arranged  on  either  side. 

The  arrangement  shown  at  d consists  of  double-throw  feeder  circuits  and  single- 
throw generator  circuits.  This  system  may  be  desirable  because  of  the  difficulty  of 
parallel  operation  where  one  set  of  generators  differs  in  characteristics  from  the  other; 
because  of  different  voltages  on  the  two  bus-bars;  or  because  one  is  alternating  and  the 
other  direct-current.  Dotted  lines  in  the  main  bus-bar  indicate  an  arrangement  for 
double-throw  generator  circuits;  in  the  exciter  bus-bars  indicate  that  arrangement  is 
made  for  parallel  operation  of  all  exciters;  in  the  instrument  and  synchroscope  bus-bars 
indicate  that  arrangement  is  made  for  using  either  set  of  instruments  for  the  station 
as  desired. 


the  quarries  where  the  selection  must  be  made  from  unpolished  marble 
of  shade  and  markings,  as  is  being  quarried  at  the  time  of  the  order. 

The  usual  arrangement  for  90-inch  panels  consists  of  a 60  to 
70-inch  upper  section  with  a 30  to  20-inch  lower  section.  Of  these 
the  combinations  of  65  and  25-inch  sections  and  62  and  28-inch 


1541 


Switchboards  For  Power  Stations 


41 


sections  are  most  used.  The  usual  combinations  for  the  three-sec- 
tioR  panels  are,  upper  20  inches,  middle  45  inches,  lower  25  inches; 
or  upper  31  inches,  middle  31  inches,  lower  28  inches. 

Black  marine  finished  slate  is  one  of  the  most  serviceable  mate- 
rials for  this  type  of  board  as  well  as  the  cheapest.  This  has  a dull 
velvety  black  finish  which  may  easily  be  kept  in  good  condition. 
The  natural  material  is  usually  purple  slate.  When  rubbed  with 
oil  this  finish  will  not  show  oil  stains.  This  feature  is  of  special  im- 
portance whereoilcircuit  breakers 
are  mounted  directly  on  the  panels 
for,  in  spite  of  all  precautions,  the 
oil  will  usually  get  on  the  panels 
sooner  or  later.  Natural  black 
slate,  the  best  of  which  comes  from 
Maine,  is  used  without  the  appli- 
cation of  any  artificial  finish  other 
than  clear  oil,  and  is  even  more 
serviceable  than  the  black  marine 
slate,  though  more  expensive. 

Black  marine  finish  is  often 
applied  to  marble  especially  when 
the  voltage  of  the  live  parts 
mounted  thereon  is  too  great  to 
permit  the  use  of  slate.  Thus 
whole  switchboards,  or  only  cer- 
tain high-voltage  sections  of  slate 
switchboards,  may  be  made  of 
black  marine  finished  marble. 

This  material  is  cheaper  than  the 
natural  polished  marble,  as  no 
polish  is  required  and  the  ma- 
terial is  usually  that  rejected  from  the  natural  finished  marbles  on 
account  of  blemishes  in  marking  and  coloring. 

Of  the  natural  finished  marble  the  blue  Vermont  is  the  best 
domestic  marble  for  switchboard  work,  owing  to  its  good  insulat- 
ing qualities  and  its  uniformity  in  coloring  and  marking.  White 
Italian  marble,  though  possessing  better  mechanical  and  electrical 
properties,  is  usually  prohibitive  on  account  of  its  cost.  Its  use 


Fig.  14 — Cost  of  Three-Phase  Switchboards 
Corresponding  to  Panel  No.  1,  Fig.  6* 

Switchboards  for  two-phase  2200  volts 
would  cost  2.5  per  cent  higher  than  the  corre- 
sponding three-phase  boards  in  capacities 
from  25  to  800  k.v.a.,  4.3  per  cent  higher  in 
capacities  from  1000  to  1200  k.v.a.  and  10  per 
cent  higher  from  1400  to  2250  k.v.a.;  for  6600 
volts  the  two-phase  boards  will  cost  2.25  per 
cent  higher  from  75  to  3500  k.v.a.  and  10  per 
cent  higher  from  4000  to  6000  k.v.a. 


*When  combining  panels  to  make  up  the  cost  of  a complete  board,  from 
this  and  the  succeeding  curves,  the  bus-bars  should  be  calculated  separately 
and  a sufficient  increase  should  be  made  in  the  cost  of  the  boards  if  the  bus-bar 
capacity  at  any  panel  exceeds  the  capacity  of  the  panel. 


42 


Switchboards  For  Power  Stations 


1541 


is  now  confined  chiefly  to  those  applications  in  which  appearance 
is  a major  consideration.  All  polished  marble  switchboards  for 
this  class  of  service  should  have  the  back  and  edges,  also  the  sides 
of  all  holes,  treated  with  an  oil-proof  varnish,  to  prevent  oil  stains 
from  discoloring  the  marble.  The  appearance  is  considerably 
improved  if  a clear  varnish  is  used,  as  the  natural  marking  of  the 
marble  is  thus  brought  out  almost  as  well  as  when  polished.  Where 


Fig.  15 — Cost  of  Three-Phase  Switchboards 

Corresponding  to  Panel  No.  2,  Fig.  6 

Switchboards  for  two-phase  2200  volts 
would  cost  1.75  per  cent  higher  than  the 
corresponding  three-phase  boards  in  ca- 
pacities from  25  to  800  k.v.a.,  3.25  per  cent 
higher  in  capacities  from  1000  to  1200  k.v.a. 
and  10  per  cent  higher  from  1400  to  2250 
k.v.a.;  for  6600  volts  the  two-phase  boards 
will  cost  1.5  per  cent  higher  from  75  to  3500 
k.v.a.,  2.8  per  cent  higher  at  4000  k.v.a.  and 
5 per  cent  higher  from  5000  to  6000  k.v.a. 


Fig.  16 — Cost  of  Three-Phase  Switchboards 

Corresponding  to  Panel  No.  3,  Fig.  6 

Switchboards  for  two-phase  2200  volts 
would  cost  6.6  per  cent  lower  than  the 
corresponding  three-phase  boards  in  capac- 
ities from  25  to  1200  k.v.a.  and  1.6  per  cent 
higher  from  1200  to  2250  k.v.a. ; for  6600  volts 
the  two-phase  boards  will  cost  6 per  cent 
lower  from  75  to  3500  k.v.a.  and  3 per  cent 
higher  from  4000  to  6000  k.v.a.  The  two 
phase  requires  but  two  ammeters  and 
therefore  a 16-inch  panel  may  be  used, 
making  the  total  price  lower  for'two  phase 
up  to  1200  k.v.a.  at  2200  volts  and  3500  k.v.a. 
at  6600  volts  when  the  change  to  the  600- 
ampere  switch  increases  the  price  to  a 
value  higher  than  that  for  the  correspond- 
ing three-phase  panel. 


current-carrying  parts  are  mounted  directly  on  the  switchboard, 
slate  can  seldom  be  used  above  6000  volts,  whereas  marble  may  be 
used  for  voltages  as  high  as  3300. 

For  the  small  boards  the  tubular  frame  is  undoubtedly  the 
best  selection.  The  lower  part  of  these  frames  which  appears  between 
the  panel  section  and  the  floor  does  not  require  any  special  covering 
to  give  a finished  appearance.  The  number  of  castings,  bolts, 
etc.,  is  small,  as  these  panels  usually  have  but  four  mounting  bolts. 


1541 


Switchboards  For  Power  Stations 


43 


and  therefore  assembly  at  the  factory,  shipment,  erection  and  altera- 
tions or  additions  are  easily  accomplished.  The  frame  for  multi- 
section panels,  however,  presents  a different  problem.  The  compari- 
son between  the  2 by  3 by  angle  frame  (Fig.  11)  and  the  \ ]/^- 

inch  tubular  frame  (Fig.  12)  is  about  as  follows: 


Cost  of  frame,  materials  for  ship- 
ment. 

Cost  of  packing,  painted  and  assem- 
bled. 

Cost  of  erecting  at  destination. 

Mechanical  strength  and  alignment 
of  panels. 


Tubular  frame  approximately  25  per 
cent  cheaper. 

Angle  frame  approximately  65  per 
cent  cheaper. 

Angle  frame  approximately  50  per 
cent  cheaper. 

Greatly  in  favor  of  angle  frame. 


Fig.  17 — Cost  of  Three-Phase  Switchboards 

Corresponding  to  Panel  No.  8,  Fig.  6 

Switchboards  for  two-phase  2200  volts 
would  cost  15  per  cent  higher  than  the 
corresponding  three-phase  boards  in  capac- 
ities from  25  to  1200  k.v.a.  and  13  per  cent 
higher  from  1400  to  2250  k.v.a.;  for  6600 
volts  the  two-phase  boards  will  cost  16  per 
cent  higher  from  75  to  3500  k.v.a.  and  13 
per  cent  higher  from  4000  to  6000  k.v.a. 


Fig.  18 — Cost  of  Three-Phase  Switchboards 
Corresponding  to  Panel  No.  9,  Fig.  6 

The  two-phase  panels  of  this  type  cost 
approximately  2.3  per  cent  more  than  the 
corresponding  three-phase  panels. 


Where  angle  frames  are  employed,  the  panel  sections  and  the 
two  panel  uprights  form  a unit,  and  may  be  handled  as  such  in 
shipping  and  erecting.  As  there  is  no  necessity  for  removing  the 
panel  sections  from  the  angle  frame  before  shipment,  the  panels 
may  be  completely  wired  by  the  manufacturer  before  delivery. 
For  the  tubular  frame,  however,  one  upright  is  common  to  two 
adjacent  panels,  and  to  pack  the  panel  as  a whole,  a temporary 
upright  must  be  supplied  with  each  panel  but  one.  This  renders  the 
packing  and  erecting  at  destination  so  much  more  difficult,  to  say 


44 


Switchboards  For  Power  Stations 


1541 


nothing  of  the  added  expense  of  the  temporary  uprights,  that  the 
tubular  frame  switchboards  are  usually  shipped  unassembled. 

Arrangement  of  Panels 

A great  number  of  the  arrangements  of  the  panels  of  a switch- 
board may  be  made,  each  possibly  with  distinctive  merits  of  its  own. 
It  is  obvious,  however,  that  as  there  are  so  many  switchboards  quite 
similar  in  design,  as  well  as  in  the  functions  which  they  perform, 
there  must  be  some  logical  arrangement  which,  in  general,  meets 


Fig.  19 — Cost  of  Three-Phase  Switchboards 
Corresponding  to  Panel  No.  11,  Fig.  6 

Prices  for  two-phase  panels  are  approxi- 
mately 3.6  per  cent  higher  than  the  corre- 
sponding three-phase  panels. 


Fig.  20 — Cost  of  Three-Phase  Switchboards 
Corresponding  to  Panels  Nos.  14,  15  and 
16,  Fig.  6 


almost  every  requirement.  Such  an  arrangement,  as  shown  in  Fig. 
13(a),  is  as  follows:  Voltage  regulator  panel  (if  any)  at  one  end  of 

board  followed  by  exciter  panels,  generator,  totalizing,  transformer 
and  feeder  panels.  Some  of  the  advantages  of  this  arrangement 
over  other  possible  arrangements  are: 

Ease  of  adding  to  the  board  without  materially  disturbing  the  existing 
panels.  By  arranging  the  panels  in  order  of  their  current  capacities,  with  the 
heaviest  capacity  panels  at  the  center  of  the  board,  the  bus-bar  copper  is  usually 
reduced  to  a minimum.  The  output  of  the  station  may  be  totalized  on  one  set 
of  meters  connected  to  bus-bar  transformers,  between  the  generator  and  the 
feeder  panels.  (When  the  generator  panels  are  separated  by  feeder  panels, 
totalizing  cannot  be  accomplished  without  undesirable  intricacies  in  wiring 
connections.)  The  alternating-current  bus-bars  do  not  cross  the  exciter  panels. 
The  exciter  bus-bars  are  of  minimum  length.  The  concentration  of  various 
panels  of  a kind  at  one  part  of  the  board  assists  the  operator  materially  by  reduc- 
ing the  number  of  steps,  and  consequently  the  time  required  for  any  switching 
operation 


1541 


Sivitchboards  For  Power  Stations 


45 


The  arrangement  of  panels  for  each  switchboard  should,  how- 
ever be  given  careful  consideration.  An  arrangement  may  then  Te 
chosen  which  will  suit  the  local  conditions  better  than  the  arrange- 
ment just  described  (see  Fig.  13  (a),  (b),  (c)  and  (d)).  The  deter- 
mining factors  to  be  considered  are: 

The  scheme  of  main  connections,  the  scheme  of  operation,  the  geography 
of  the  station  apparatus,  the  arrangement  of  cables  to  and  from  the  switchboard, 
the  desirability  of  totalizing  the  load,  and  future  additions. 

Less  attention  is  usually  given  to  the  arrangement  of  cables 
than  their  importance  warrants.  It  is  not  unusual  to  find  arrange- 


Ann 

1 

r 

PANELS  Nos.  17,  18  AND  19-nC.  6 

Cost  in  Cents  per  K.  V.  A. 

f ffA 

Cap! 
K.  V. 

A. 

No.  17 

No.  18 

No.  19 

10 

20 

30 

40 

50 

60 

75 

100 

200 

250 

300 

400 

500 

600 

800 

1000 

1200 

910 

455 

303.3 

227.5 
182 

151.6 

121.3 
91 

45.5 
40 
33.3 
25 

20.5 
17.1 
12.8 

11.5 
9.5 

1330 

665 

443.3 

332.5 
266 

221.6 

177.3 
133 

66.5 

57.2 

47.6 

35.6 
28.8 

24.3 
18.2 

15.6 
13 

1490 

745 

496.6 

372.5 
298 
248.3 

198.6 
149  , 

74.5 

63.6 
53 

39.7 

32.2 

27.1 

20.3 

17.2 

14.3 

1 

\ 

< 

\ 

17 

> 

V 

k 

-18 

^.0 

\ 

\ 

■19 

1 (M? 

-50- 

2 

) ? 

> K 

0 

Cents 

5 1[ 

£nj< 

9 1 

V, , 

'5  2i 

<3  . 

0 2; 

S 2 

0 i 

PANELS  Nos.  20,  21  AND  22-FIG.  6 

K.V.A 

Cost  in  Cents  per  K V A 

No  20 

No  21 

No  22 

10 

20 

30 

40 

50 

60 

75 

100 

200 

250 

300 

400 

500 

600 

800 

1000 

1200 

870 

435 

290 

217.5 

174 

145 

116 

87 

43.5 

34.8 

29 

21.7 

17.4 

14.5 

10.8 
8.7 
7.2 

340 

170 

113.3 

85 

68 

56.6 
45.3 
34 
17 

17.2 

14.3 

10.7 
8.8 
7.3 
5.5 

5.2 

4.3 

630 
. 315 
210 
157.5 
126 
105 
84 
63 
31.5 

At^(\ 

<c 

> 

1 

40 

\ 

“250 

- ^ 

2l 

200 

\ \ 

"lOO 

2^-3 

[T^ 

5 1 

WT: 

|nls 

K \( 

r5  2 
A 

>0^ 

/b 

Fig.  21 — Cost  of  Three-Phase  Switchboards 

Corresponding  to  Panels  Nos.  17,  18  and 

19,  Fig.  6 

Prices  for  two-phase  2200-volt  board 
of  the  type  corresponding  to  panel  17  will 
be  0.5  per  cent  higher  than  the  correspond- 
ing three-phase  panel  from  10  to  200  k.v.a. 
and  6 per  cent  higher  from  200  to  1200  k.v.a.; 
for  panel  18,  0.5  per  cent  higher  from  10  to 
800  k.v.a.  and  approximately  the  same  price 
above  1000  k.v.a.;  for  panel  19  approximate- 
ly 0.5  per  cent  higher  throughout.  The 
prices  for  two-phase  and  three-phase  pan- 
els of  these  types  are  almost  identical 
owing  to  the  fact  that  a narrower  panel 
and  but  two  ammeters  for  two-phase  offset 
the  four-pole  breaker  and  additional 
wiring. 


Fig.  22 — Cost  of  Three-Phase  Switchboard 
Corresponding  to  Panels  Nos.  20,  21  and 
22,  Fig.  6 

Prices  for  a two-phase  board  of  the  type 
corresponding  to  panel  20,  Fig.  6,  are  approx- 
imately 8 per  cent  higher  than  for  the 
corresponding  three-phase  panel;  for  panel 
21,  6 per  cent  higher  from  10  to  200  k.v.a., 
and  16  per  cent  higher  from  250  to  1200 
k.v.a.;  and  for  panel  22,  11  per  cent  higher. 


ments  which  save  copper  in  the  bus-bars  at  the  expense  of  increase 
in  the  cost  of  cable.  Later  additions  are  often  made  at  excessive 
cost  and  great  inconvenience  to  the  operation  of  the  station.  Blank 
panels  properly  located  during  the  initial  installation  usually  save 
many  times  their  cost.  A carefully  prearranged  scheme  of  inter- 


46 


Switchboards  For  Power  Stations 


1541 


changing  panels  may,  however,  permit  the  making  of  all  necessary 
additions.  For  example,  the  bus-bars,  instrument  transformer 
supports  and  all  openings  in  the  floor  may  be  arranged  so  that  they 
will  suitably  accommodate  future  additions. 

Arrangement  of  Apparatus 

The  usual  arrangement  of  apparatus  on  individual  panels  as 
recommended  by  best  practice  is  shown  in  Fig.  6.  Some  operators 
prefer  arrangements  which  differ,  more  or  less,  from  those  illus- 
trated, and  in  some  cases  the  conditions  may  warrant  radical  depar- 
tures, but  if  the  following  requirements  are  complied  with  it  will 
usually  be  seen  that  the  arrangements  illustrated  are  obtained : 


Fig.  23  Fig.  24 


Fig.  23 — Single  Generator  Rheostat  Supported  from  Back  of  Panel  by  a Single  Bracket 

Fig.  24 — Generator  and  Exciter  Rheostat  Mounted  in  Combination  and  Supported  from 

Single  Bracket 

Fig.  25 — Combination  Mounting  of  Handwheels  with  Generator  Rheostat  Mounted  Near 
Either  Top  or  Bottom  of  Board;  Exciter  Rheostat  on  Single  Bracket 


1 —  Indicating  instruments  should  be  mounted  at  or  a little  above  the 

height  of  the  eyes. 

2 —  Meters  of  a kind  (for  example,  ammeters)  should  be  symmetrically 

grouped  on  the  panel  so  that  phase  distinctions  are  apparent. 

3 —  Meters  of  a kind  should  be  in  alignment  with  each  other  on  the  various 
, panels,  for  convenience,  appearance  and  symmetry  of  wiring. 

4 —  Voltmeter  receptacles  and  similar  plugging  devices  should  be  located 

as  near  the  instruments  as  possible  to  simplify  and  decrease  amount 
of  small  wiring. 

5 —  Rheostats,  unless  very  small,  should  be  sprocket  operated,  the  face 

plates  and  resistance  mounted  as  a unit  and  located  in  some  con- 
venient place  where  the  contacts  may  readily  be  inspected  and  where 
the  heat  from  the  resistance  will  do  no  harm.  The  handwheels 
should  be  located  near  the  center  of  the  panel  at  such  a height  that 
the  operator  may  readily  watch  his  instruments  while  adjusting 
the  rheostat  and  can  have  one  hand  free  to  operate  the  voltmeter 
receptacle,  field  switch  or  main  switch. 


1541 


Switchboards  For  Power  Stations 


47 


6 —  The  main  switches  or  circuit-breakers  should  be  located  at  a height 

most  convenient  for  ease  in  operation.  They  must  not  be  so  close 
to  the  edge  of  the  panel  section  as  to  interfere  with  the  frame  work 
or  to  give  insufficient  distance  to  the  adjacent  apparatus,  or  so  near 
the  floor  as  to  prevent  free  removal  of  the  tanks  for  inspection. 

7 —  Watthour  meters  or  relays  may  be  mounted  on  the  subsections  or  at 

the  rear  of  the  board,  as  they  require  only  occasional  attention. 

8 —  High-tension  bus-bars  should  be  mounted  near  the  top  of  the  board 

to  avoid  accidental  contact,  thus  obviating  the  necessity  of  insulating 
them  to  prevent  injury  to  attendants.  This  arrangement  also  per- 
mits free  access  to  the  rear  of  the  board. 

9 —  Voltage  and  current  transformers  may  be  mounted  at  the  rear  of  the 

board  on  suitable  supports,  but  usually  at  the  expense  of  accessibility 
to  the  instrument  wiring  and  auxiliaries  mounted  on  the  back  of  the 
panel,  and  of  the  general  appearance  of  the  installation.  It  is  recom- 
mended that  they  be  placed  apart  from  the  board  wherever  possible, 
(see  Fig.  9);  beneath  the  floor  if  the  leads  go  down,  or  on  the  wall 
where  they  go  up. 

10 — Such  instruments  as  graphic  recording  meters,  static  ground  detectors 
and  voltage  regulators  should  not  be  placed  on  swinging  brackets  or 
swinging  panels. 


Costs 

The  curves  with  tables,  Figs.  14  to  22  inclusive,  showing  the 
cost  in  cents  per  kilovoltampere  capacity,  will  indicate  the  relative 
costs  of  the  various  panel  arrangements  and  of  the  comparative  cost 
of  2200  and  6600-volt  panels.  The  figures  given  include  all  wiring 
details,  and  bus-bars  of  the  rated  capacity  of  the  panels.  The  tables 
permit  a more  accurate  interpretation  of  the  curves  and  also  indicate 
the  values  beyond  those  shown  by  the  curves.  The  irregularities  and 
breaks  in  the  curves  are  occasioned  by  the  fact  that  two  sizes  of  oil 
switch  are  involved,  namely  the  300  and  600-ampere  capacities.  The 
change  in  capacity  for  this  rating  comes  between  1200  and  1400 
kilowatts  for  2200-volt  panels,  and  between  3000  and  4000-kilowatt 
capacity  for  6600  volts.  As  shown  by  the  curves  the  prices  of  the 
generator  panels  are  usually  the  same,  regardless  of  k.v.a.  capacity, 
up  to  500  or  800  k.v.a.  Above  these  capacities  they  increase  by 
steps  owing  to  additional  cost  of  current  transformers,  panel  wiring 
etc.,  until  the  sudden  change  to  the  higher  capacity  switches  causes  a 
break  in  the  curve.  The  two-phase  panels  usually  exceed  the  three- 
phase  panels  in  cost  by  the  cost  of  the  extra  circuit-breaker  pole  and 
its  wiring,  but  this  is  not  true  where  three  ammeters  are  used  for 
three  phases  and  two  for  two  phases,  as  the  fewer  meters  and  the 
narrower  panel  may  make  the  two-phase  cheaper  than  the  three- 
phase  panel. 


48 


Switchboards  For  Power  Stations 


1541 


Rear  of  Board 

The  design  of  the  rear  of  a switchboard  is  a good  indication  of 
its  real  worth  as  an  engineering  production.  Even  more  care  is 
necessary  than  for  the  front,  as  it  is  here  that  switchboard  troubles 
most  usually  occur,  and  the  chance  of  their  occurrence  is  multi- 
plied if  a careless  or  inconsistent  design  is  adopted.  It  is  a com- 
paratively simple  matter  to  produce  a well-arranged,  well-appearing 
front,  but  the  rear  of  the  board  with  its  many  details,  forming  a 
combination  of  high  and  low-voltage  conductors,  moving  mechanical 
parts,  instrument  and  control  wiring,  oil  circuit-breakers,  rheostats, 
etc.,  presents  a problem  which  requires  originality  and  systematic 
design  on  the  part  of  the  engineer  and  a skilled  and  patient  draughts- 


Fig.  26  Fig.  27  Fig.  28 


Fig.  26 — Same  as  Fig.  25  Excej^t  Generator  Rheostat  is  Mounted  on  the  Floor  or  Supported 

From  the  Ceiling 

Fig.  27 — Remote  Control  Wall  Mounting  of  Large  Generator  Rheostat  Showing  three 
Good  Methods  of  Arranging  the  Control 

Fig.  28 — Handwheel  of  Generator  and  Exciter  Rheostat  Mounted  in  Combination; 
Both  Rheostats  Remote-Controlled 


man.  This  is  probably  more  true  of  the  self-contained  switchboard 
than  of  any  other,  as  the  greater  part  if  not  all,  of  the  auxiliary 
apparatus  is  mounted  upon  or  supported  from  the  rear  of  the  board. 
This  auxiliary  apparatus  consists  chiefly  of  bus-bars,  instrument 
wiring,  instrument  transformers,  fuse  blocks  and  fuses,  main  inter- 
connections with  their  supports,  instrument  and  discharge  resistances 
and  rheostats,  but  very  often  it  is  necessary  that  space  be  found  for 
disconnecting  switches,  fuses  for  main  circuits,  wattmeters  and  relays. 
This  is  obviously  bad  engineering  and  should  be  avoided  by  finding 
room  for  much  of  the  high-voltage  apparatus,  such  as  instrument 
transformers,  disconnecting  switches  and  fuses  away  from  the  board 
itself  (Fig.  9).  This  treatment  permits  an  accessible,  open  arrange- 


1541 


Switchboards  For  Power  Stations 


49 


mcnt  of  the  main  and  control  wiring  and  other  apparatus  which 
should  naturally  be  mounted  on  the  back  of  the  panels. 

Rheostats,  when  small,  are  best  located  at  the  rear  of  the  board, 
preferably  supported  on  brackets  which  will  not  materially  de- 
crease the  space  required  for  instrument  wiring  and  other  details 
(Fig.  23).  When  individual  exciters  are  used  with  the  generators 
their  rheostats  may  be  mounted  in  combination,  the  handwheels 
being  eccentric  on  the  front  of  the  panel,  the  main  rheostat  being 
controlled  by  means  of  a hollow  shaft  which  contains  the  shaft  of 
the  exciter  rheostat  (Fig.  24). 

Where  the  size  of  the  rheostats  precludes  the  combination 
mounting,  the  concentric  handwheels  may  still  be  retained  by  mak- 


Fig.  29 — Suggested  Arrangement  for  Large  Remote-Controlled  Rheostats 


ing  the  main  rheostat  sprocket  operated,  and  locating  it  near  the 
top  or  bottom  of  the  panel  (Fig.  25).  The  larger  capacity  rheo- 
stats, whose  resistance  must  be  made  up  of  cast-iron  grids,  should 
be  mounted  entirely  independent  of  the  board  (Fig.  26).  It  is  not 
good  practice  to  mount  the  face-plate  at  the  board  and  the  resist- 
ance apart  from  it  because  of  the  great  number  of  cables  required 
to  connect  one  to  the  other,  a 48-step  face-plate,  for  example,  re- 
quiring 49  leads.  The  better  method  is  to  mount  the  face  plate 
as  indicated  in  Figs.  28  and  29. 

Cables  to  and  from  the  switchboard  should  be  supported  in 
such  a manner  that  their  weight  will  not  be  suspended  from  a soldered 
joint  or  the  terminal  of  a circuit-breaker.  Cables  should  not  be  used 


50 


Switchboards  For  Power  Stations 


1541 


as  connections  for  switchboard  apparatus  where  bends  are  necessi- 
tated, as  they  will  not  keep  their  form  unless  carefully  supported  or 
enclosed  in  a stiff  covering.  Connections  are  preferably  made  of 
flame-proof  solid  wire,  well  insulated  against  accidental  contact.  If 
the  connection  is  of  too  large  capacity  to  be  made  with  one  0000  wire, 
and  it  is  inadvisable  to  use  two  or  more,  bare  copper  rods,  tubes  or 
straps  should  be  used.  This  should  be  well  insulated  after  erection 
with  varnished  cambric  tape  or  its  equivalent,  to  protect  against 
accidental  contact,  and  it  is  advisable  to  flame-proof  all  such  insula- 
tion with  asbestos  tape  or  some  equivalent.  To  give  it  permanency 
the  asbestos  tape  should  be  treated  with  a binding  solution  such  as 
silicate  of  soda.  Practically  all  switch-board-mounted  circuit- 
breakers  are  now  designed  so  that  their  terminals  may  be  conven- 
iently insulated  by  taping  or  by  removable  tubes.  When  tubes  are 
used  the  connection  to  the  circuit-breaker  must  rise  vertically  the 
height  of  this  tube  to  permit  access  to  the  terminals. 

All  connections,  both  main  and  auxiliary,  should,  when  at  all 
possible,  be  run  vertically  and  horizontally  with  right-angle  bends 
made  to  a sufficient  radius,  so  that  the  conductor  will  not  be  in- 
jured. The  same  suggestion  applies  to  any  straps,  brackets,  braces 
or  other  members  of  the  switchboard  construction,  for  the  appear- 
ance of  the  board  is  very  greatly  bettered  thereby.  This  rule  is 
of  further  advantage  in  producing  a uniform  spacing  throughout  if 
properly  executed,  whereas  any  other  method  will  result  in  many 
of  the  conductors  being  much  closer  together  at  some  places  than 
at  others.  This  results  either  in  the  loss  of  the  factor  of  safety  in 
insulating  distance,  or  an  increase  in  the  depth  of  the  entire  arrange- 
ment. 


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Switchboards  For  Power  Stations 


51 


Fig.  1 — Switchboard  of  Medium  Size 

For  controlling  two  exciters,  two  generators,  and  one  feeder  as  shown  in  Fig.  3.  An 
alternating-current  ammeter,  voltmeter,  indicating  wattmeter,  power  factor  meter,  and 
field  ammeter  are  used  for  each  generator  with  watthour  meter  mounted  on  the  rear  of 
the  panel.  The  motor  panel  accommodates  the  voltage  regulator  as  well  as  the  circuit- 
breaker  handle  and  ammeter  for  the  motor.  The  exciters  have  individual  ammeters 
and  a common  voltmeter,  while  the  feeder  is  provided  with  a graphic  indicating  watt- 
meter and  a polyphase  watthour  meter. 

that  their  use  has  become  very  frequent.  In  many  cases  they  are 
given  preference  over  the  self-contained  or  the  electrically  operated 
designs,  owing  either  to  the  many  desirable  features  secured  with 
very  little  increase  in  cost,  or  to  the  fact  that  for  many  installations 


REMOTE  MECHANICALLY-CONTROLLED 
SWITCHBOARDS 


By  C.  H.  SANDERSON 


The  many  advantages  to  be  gained  from  the  use  of  the  remote 
mechanically-controlled  type  of  switching  apparatus  have  been  so 
readily  recognized  by  those  having  switchboard  problems  to  solve 


52 


Switchboards  For  Power  Stations 


1541 


the  remote  mechanical  control  provides  the  same  desirable  operating 
features  as  may  be  obtained  by  the  use  of  electrically-operated 
switching  apparatus  with  a great  decrease  in  cost. 


Fig.  2 — Rear  View  of  Switchboard  Shown  in  Fig.  1 


The  watthour  meters  for  the  generator,  motor,  and  feeder  circuits  are  mounted  on 
short  brackets  at  the  top  of  the  board  above  the  direct-current  field  bus.  The  shunts 
of  the  exciter  ammeter,  at  left  of  board,  are  mounted  on  a slate  base.  The  equalizer 
rheostat  is  mounted  on  the  sub-paneJ.  The  next  panel  contains  the  voltage  regulator 
resistances,  with  condensers  and  brackets  for  circuit-breaker  relays  mounted  beneath. 
The  two  generator  panels  contain  the  field-ammeter  shunt,  sprockets  and  idlers  for  the 
rheostat,  controller  for  engine  governor  motor,  and  ammeter  receptacles. 

Remote  mechanical  control  of  switching  apparatus  was  perhaps 
first  used  in  connection  with  high-voltage  carbon  circuit-breakers. 
Before  the  advent  of  the  oil  circuit-breaker,  alternating  current 
circuits  above  600  volts  were  commonly  opened  with  carbon  breakers 
which  were  usually  separated  by  large  fireproof  barriers.  They 
were  mounted  at  the  top  of  very  high  panels  so  as  to  protect  the 
attendants  against  accidental  contact.  Remote  mechanical  control 
was  thus  necessitated,  and  the  convenience  and  safety  secured  by  its 


1541 


Switchboards  For  Power  Stations 


53 


use  soon  led  to  the  removal  of  dangerous  or  bulky  apparatus  from 
the  switchboard  panels.  The  first  oil-circuit-breakers  were  of  such 
design  and  capacity  as  to  be  easily  adapted  to  switchboard  mounting 
However,  the  demand  for  larger  generating  units  and  higher  voltages 
soon  necessitated  circuit-breakers  of  a size  and  weight  suitable 
only  for  separate  mounting. 

So  great  has  been  the 
demand  for  hand-oper- 
ated remote-controlled 
switching  apparatus  that 
practically  all  switching 
apparatus,  regardless  of 
size  or  capacity,  may 
now  be  obtained  suitably 
arranged  for  remote  man- 
ual operation.  Many  of 
the  plants  of  smaller  ca- 
pacity which  could  read- 
ily have  used  panel- 
mounted  apparatus  have 
felt  justified  in  incurring 
the  small  extra  expense 
necessary  to  provide  the 
remote  mechanically- 
controlled  equipment. 

Many  of  the  large  central  stations  and  transmission  companies, 
while  using  electrically  operated  equipments  in  their  main  gener- 
ating and  transforming  stations,  have  adopted  remote  control  for 
the  same  class  of  apparatus  in  their  sub-stations. 

Advantages 

The  advantages  gained  by  the  use  of  remote  mechanical  control 
over  that  of  the  self-contained  boards  may  be  summarized  briefly 
as  follows: 

1 —  All  high  voltages  are  removed  from  the  panels,  thus  per- 
mitting ready  inspection  of  the  instrument  and  control  wiring, 
eliminating  danger  of  injury  to  attendants  from  contact  with  live 
parts,  permitting  the  location  of  the  board  to  much  better  advan- 
tage as  regards  the  remainder  of  the  installation  because  less  space 
and  less  protection  are  required. 

2 —  Panels  are  not  subject  to  the  mechanical  strains  due  to 
automatic  operation  or  to  the  dead  weight  of  the  apparatus. 


Sh.  Fid. 

Fig.  3 — Diagram  of  Connections  for  Switchboard 
Shown  in  Figs.  1 and  2 


54 


Switchboards  For  Power  Stations 


1541 


3 —  In  case  of  marble  panels  their  appearance  is  not  marred 
by  stains  from  creeping  oil. 

4 —  Violent  explosions  which  sometimes  occur  upon  the  opening 
of  heavy  currents  or  the  possible  failure  of  a circuit-breaker  will  not 
injure  the  panels  and,  if  the  circuit-breakers  are  sufficiently  spaced 
or  are  enclosed  in  fireproof  cells,  adjacent  circuit-breakers  will  not 
be  affected. 

5 —  The  panels  may  be  much  narrower,  the  reduced  cost  thereof 
offsetting,  to  a considerable  extent,  the  additional  cost  of  the  remote- 


control  feature.  Moreover,  the  decrease  in  total  length  of  the  board 
may  result  in  a very  material  saving  in  cost. 

6 —  A more  compact  arrangement  of  the  apparatus  is  ofgreat  as- 
sistance to  the  operator,  approaching  as  it  does  more  nearly  to  the  com- 
pact and  efficient  arrangements  obtained  by  means  of  control  desks. 

7 —  Much  shorter  main  connections  are  made  possible,  and 
high  voltages  kept  away  from  certain  floors,  or  certain  rooms  by 
locating  the  remote-control  structure  properly. 


Meters 


Fig.  4 — Large  Remote-Control  Switchboard 


For  light  and  power  distribution,  controlling  apparatus  as  shown  in  Fig.  6. 
are'provided  with  black-faced  dials  with  white  lettering. 


1541 


Switchboards  For  Power  Stations 


55 


8 —  Where  a wall  is  used  for  supporting  the  apparatus,  the 
cost  of  the  complete  outfit  may  be  reduced  to  very  near  that  of 
the  self-contained  type  of  board,  and,  in  some  cases  of  very  heavy 
capacities  at  low  voltages,  may  be  less  in  cost.  Moreover,  accessible 
arrangements  of  apparatus  with  ample  spacings  may  easily  be 
obtained. 

9 —  Where  a steel  or  masonry  structure  is  used,  access  may 
be  had  to  either  side  of  the  structure  and  an  arrangement  of  this 


Fig.  5 — Rear  View  of  Switchboard  Shown  in  Fig.  4 

The  calibrating  receptacles  may  be  seen  near  the  bottom  of  the  alternating-current 
panels,  with  the  relays  just  above  them.  On  the  exciter  panels  are  shown  the  double 
exciter  bus,  direct-current  watthour  meter  and  equalizing  rheostat. 


kind  will  satisfactorily  accommodate  the  maximum  amount  of  appara- 
tus ordinarily  used  for  either  single  or  double-throw  arrangements. 

In  comparison  with  the  electrically  operated  board,  the  remote 
mechanically-operated  board  usually  occupies  from  5 to  50  per  cent 
more  space  although  the  circuit-breakers  and  bus-bars  for  a given 
capacity  will  be  practically  identical.  The  size  of  the  board  in  either 
case  depends  primarily  on  the  number  of  instruments  employed  for 
each  circuit,  as  they  require  more  width  than  the  control  handles  of 


56 


Switchboards  For  Power  Stations 


1541 


the  circuit-breakers.  The  boards  themselves  may  be  identical 
throughout  as  to  equipment  except  for  the  method  of  control  of  the 
circuit-breakers  and  usual  attendant  difference  in  method  of  auto- 
matic relay  tripping  of  the  circuit-breakers,  the  electrically-operated 
boards  using  direct  current,  and  the  remote  mechanical  control  alter- 
nating current  for  this  purpose. 

Application 

The  remote  mechanically-controlled  switchboard  is  limited  in 
capacity  by  physical  rather  than  electrical  characteristics.  As  nearly 
all  high-capacity  circuit-breakers  may  be  arranged  for  remote  me- 
chanical control  as  well  as  electrical  operation,  the  problem  becomes 
one  of  mechanical  arrangement  in  which  it  is  usually  very  easy  to 
meet  the  electrical  requirements.  The  principal  rules  to  be  observed 
as  regards  the  mechanical  limitations  may  be  stated  briefly  as  follows : 


Fig.  6 — Single-Line  Diagram  of  Connections  of  Switchboard  Shown  in  Figs.  4 and  5 


A circuit-breaker  should  close  readily  with  the  ordinary  effort 
exerted  by  the  average  man.  It  is  impracticable  to  operate  a circuit- 
breaker  satisfactorily  when  the  total  length  of  operating  rods  exceeds 
approximately  50  feet.  In  general,  a horizontal  distance  much  in 
excess  of  35  feet  or  a vertical  distance  of  20  feet  should  not  be  exceed- 
ed with  standard  commercial  apparatus.  This  distance  may  prove 
too  great  for  satisfactory  operation,  especially  for  the  larger  sizes  of 
breakers,  if  more  than  two  bell-cranks  must  be  used  or  if  the  direc- 
tion of  motion  must  be  changed,  as  in  clearing  columns  or  other 
obstructions.  The  inertia  of  the  mechanism  should  not  be  sufficient 
to  materially  affect  the  time  or  power  required  to  close  the  breaker. 
The  mechanism  should  be  so  arranged,  if  possible,  that  rods  are  in 
tension  when  the  breaker  is  being  closed. 

When  the  mechanism  operates  vertically,  as  when  controlling 
circuit-breakers  on  floors  above  or  below  the  switchboard,  the  mech- 


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57 


anism  may  be  counterweighted  to  take  the  weight  of  the  vertical  rod 
off  the  operating  handle;  but,  as  the  inertia  of  the  mechanism  is 
thereby  increased,  the  application  of  counterweights  is  limited. 

In  view  of  these  considerations  it  is  recommended  that  this  type 
of  switchboard  be  confined  to  the  use  of  circuit-breakers  of  3000  am- 
peres capacity  or  less  and  of  35000  volts  or  less,  and  to  stations  whose 
capacity  does  not  exceed  25000  k.v.a.,  three-phase. 


Fig.  7 — Lighting  and  Power  Alternating  and  Direct-Current  Switchboard  for  Small  City 

This  is  an  unusually  compact  form  of  board  for  the  apparatus  it  controls,  as  shown 
in  the  diagram,  Fig.  9. 

Types 

The  multi-section  panel  90  inches  high  is  almost  universally 
used  for  this  class  of  board.  The  installation  which  requires  the  use 
of  remote  control  apparatus  is  of  such  capacity  that  the  smaller  type 
of  board  would  not  be  in  keeping  with  the  remainder  of  the  equip- 
ment. For  individual  circuits  or  very  small  substations,  or  when 


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associated  with  smaller  direct-current  boards,  however,  the  smaller 
type  of  panel  may  be  employed  economically  and  to  good  advantage. 

Figures  1,  2 and  3 illustrate  the  type  of  board  often  used  for  a 
hydro-electric  plant  of  medium  size  where  all  the  power  generated 
is  taken  over  one  feeder  to  the  center  of  distribution.  The  exciters 
which  are  operated  in  connection  with  a voltage  regulator,  are  con- 
trolled from  a double-exciter  panel  containing  the  ammeters,  a 


Fig.  8 — Rear  View  of  Switchboard  Shown  in  Fig.  7 

The  small  amount  of  space  occupied  and  the  accessibility  of  all  parts  are  clearly 
shown. 

common  voltmeter,  main  and  equalizing  rheostats,  and  main 
switches.  The  second  panel  contains  the  handles  for  the  automatic 
protective  circuit-breaker  and  the  starting  circuit-breaker,  and  the 
ammeter  for  the  exciter  motor,  as  well  as  the  regulator.  The  two 
generator  panels  are  each  equipped  with  ammeter,  voltmeter,  power 
factor  meter,  indicating  wattmeter  and  held  ammeter,  and  the  usual 
switches,  circuit-breaker  handle,  plugs  and  receptacle  with  the  addi- 


IPaoel  No.  ,U/  Pan 


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Switchboards  For  Power  Stations 


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9 — Complete  Diagram  of  Connections  for  Switchboard  Shown  in  Figs.  7 and  8 

Two  synchronous  motors  are  controlled  from  one  panel  No.  6,  24  inches  wide,  with  sufficient  space  reserved  for  a third.  Two  generators  are  con- 
trolled from  panel  No.  10,  16  inches  wide,  with  panel  No.  9 reserved  for  two* future  generators.  Each  of  the  16-inch  feeder  panels  controls  two  feeders. 
The  direct-current,  three-wire  generators  are  protected  by  series  relays  connected  directly  to  the  armature  circuits. 


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Switchboards  For  Power  Stations 


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tion  of  a governor  speed  controller.  The  feeder  is  provided  with  a 
graphic  wattmeter  and  an  automatic  circuit-breaker  with  relays,  the 
latter  usually  inverse  or  definite  time  limit,  but  often  reverse  power 
where  the  station  feeds  into  a system  of  power  stations. 

Boards  for  large  industrial,  or  light  and  power  plants  are 
illustrated  in  Figs.  4,  5 and  6.  This  particular  equipment  is  mainly 
double  throw,  as  illustrated  in  Fig.  6.  The  meters  are  all  provided 
with  black  dials  with  white  scales  and  lettering,  which  are  generally 
considered  much  easier  to  read  than  the  white  dial.  The  bracket 
instruments,  which  are  mounted  on  a swinging  panel,  consist  of  two 
voltmeters,  a synchroscope,  power  factor  meter  and  frequency  meter. 
The  generator  panels  are  each  equipped  with  two  ammeters,  indicat- 


Fig.  10 — Remote-Control  Switchboard 


Instrument  buses  taped  in  one  group.  Auxiliary  knife  switches  for  instrument 
leads  mounted  above  and  connected  to  oil  circuit-breaker  handles.  Conduits  for  instru- 
ment wires  taken  through  channel  base  of  switchboard.  Extreme  depth  of  board  over  all, 
18  inches. 


ing  wattmeter,  voltmeter,  field  ammeter,  watthour  meter;  while  the 
feeder  panels  each  have  one  ammeter  with  receptacles  for  each  phase, 
and  a watthour  meter.  Two  good  methods  of  mounting  watthour 
meters  are  illustrated  in  Figs.  2 and  4,  the  former  on  brackets  at  the 
rear  of  the  board  near  the  top  and  the  latter  on  the  front  on  sub- 
sections. Fig.  5 shows  the  usual  method  of  mounting  relays  and 
calibrating  receptacles  at  the  rear  of  the  board. 

The  switchboard  illustrated  in  Figs.  7,  8 and  9 is  a good  example 
of  the  compact,  yet  efficient,  arrangement  which  this  class  of  board 
affords.  Sub-section  mounting  of  relays  on  the  front  of  the  board 
is  shown  in  Fig.  7. 


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Switchboards  For  Power  Stations 


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Fig.  12 — Control  Desk  and  Instrument  Panels  Equipped  for  Remote  Mechanical 

Control 

are  lost  in  a properly  designed  desk  for  remote  mechanical  con- 
trol and,  as  the  cost  does  not  greatly  exceed  that  of  the  panel  type, 
there  is  no  reason  why  it  should  not  be  chosen  for  stations  requiring 
a large  control  equipment. 


The  control  desk  (Figs  11  and  12),  though  not  yet  used  to 
any  considerable  extent  when  mechanical  control  is  employed, 
is  very  popular  for  controlling  electrically-operated  equipments 
because  of  its  many  desirable  features.  Few  of  these  features 


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IV 

REMOTE  MECHANICALLY  - CONTROLLED 
SWITCHBOARDS— Continued 

By  C.  H.  ANDERSON 

Choice  of  Arrangement  for  Circuit-Breaker  Structure 

The  choice  of  the  proper  form  of  structure  for  the  apparatus 
which  is  to  be  remote  controlled  and  the  satisfactory  arrangement 
of  the  apparatus  thereon  presents  a more  difficult  problem  than  does 
the  design  and  arrangement  of  the  panels  themselves.  The  reason 
lies  in  the  many  practical  forms  of  structure,  and  the  large  number  of 
arrangements  of  the  apparatus  which  may  be  made  upon  each  of  the 
various  forms.  For  example,  there  are,  first,  the  single-throw  and 
double-throw  systems.  Under  each  of  these  the  following  arrange- 
ments are  commonly  employed:  ' 


Fig.  1 — Wall  Mounting  Arrangement  for  Un-  Fig.  2 — Separate  Mounting  Arrange- 
enclosed  Circuit- Breakers  and  Bus-Bars  ment  With  Brace  to  Wall 

1 —  Wall  Mounting — -All  apparatus  and  bus-bars  either  mounted  directly  on 
or  supported  from  a wall  of  the  building  (Fig.  1). 

2 —  Framework  Mounting — All  apparatus  and  bus-bars  mounted  on  a frame- 
work of  iron  pipe  or  structural  steel  shapes,  or  a combination  of  the  two  (Figs. 
2 and  3). 

3—  Combination  Wall  and  Framework  Mounting — As  illustrated  by  Figs. 
4,  5 and  6. 

4 —  Concrete  or  Masonry  Structure  Mounting — All  apparatus  and  bus-bars 
mounted  in  cells  or  compartments,  as  shown  in  Figs.  7,  8 and  10. 

5 —  Combination  Concrete  and  Structural  Mounting — Circuit-Breakers 
in  concrete  cells,  remaining  apparatus  on  iron  framework,  Fig.  9. 


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Switchboards  For  Power  Stations 


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Many  modifications  of  these  arrangements  are  made  as  the 
conditions  and  surroundings  warrant.  Cells  of  asbestos  lumber, 
slate,  soapstone,  moulded  concrete  or  other  suitable  material  are 
frequently  used  to  enclose  all  or  a part  of  the  circuit-breaker  where 
schemes  1 or  2 are  employed.  The  remote-control  structure  may 
be  divided  into  two  parts;  the  circuit-breakers  for  example,  being 
mounted  on  the  switchboard  room  floor  with  the  bus-bars  and 
auxiliary  apparatus  mounted  in  the  room  beneath. 

The  following  apparatus  must  usually  be  considered  in  choos- 
ing a satisfactory  arrangement;  Circuit-breakers,  bus-bars  and 
connections,  rheostats,  instrument  transformers,  fuses  for  potential 


Fig.  3 — A Motor-Generator  Substation  Switching  Equipment  for  1,500-volt  Direct-Current 

Railway 

Showing  arrangement  of  starting  and  main  alternating-current  bus-bars  (Piedmont 
Traction  Co.),  and  assembly  of  all  disconnecting  switches  and  instrument  transformers 
on  the  tubular  framework.  The  control  for  rheostats,  as  well  as  circuit-breakers,  is 
taken  beneath  a section  of  removable  flooring.  The  direct-current  circuit-breakers 
are  also  remote  controlled  from  the  middle  section  of  the  board,  the  switches  being 
mounted  on  separate  braces  at  the  rear,  near  the  top  of  the  board. 

transformer  primaries  and  for  main  wiring  when  employed,  and  dis- 
connecting switches.  Before  a proper  choice  can  be  made,  a con- 
plete  diagram,  including  all  main  wiring  and  all  of  the  above  appara- 
tus, should  be  carefully  made,  according  to  the  system  of  connections 
which  has  been  adopted  for  the  installation  under  consideration. 


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From  this  wiring  diagram  should  be  selected  the  circuit  which  pre- 
sents the  most  complications;  that  is,  the  greatest  number  of  dis- 
connecting switches,  instrument  transformers,  etc.,  and,  with  the 
various  practical  forms  of  structure  in  mind,  an  arrangement  should 
be  worked  out  for  this  unit  of  the  structure.  If  the  remaining  circuits 
have  the  same,  or  a less  number  of  members  in  the  same  relative 
location  in  the  circuit  as  regards  the  oil  circuit-breakers,  the  problem 
is  solved  and  the  remainder  of  the  work  is  simply  duplication.  If 
the  members  in  some  circuits  appear  in  other  locations  than  those 
in  the  circuit  chosen,  each  differing  unit  must  be  worked  out  indi- 
vidually, with  a view,  however, 
of  forming  them  into  a sym- 
metrical and  uniformstructure. 

The  choice  of  arrangement 
depends  upon  the  capacity  of 
the  station,  the  cost  the 
available  space,  the  voltage, 
the  type  of  circuit-breaker 
chosen,  and  the  current  capac- 
ity of  individual  circuits. 

Discussion 

The  capacity  of  the  station, 
that  is,  the  entire  amount  of 
energy  which  can  be  concen- 
trated on  the  bus-bars,  decides 
the  capacity  of  circuit-breaker 
to  be  used  and  the  capacity 
and  design  of  the  bus-bars, 
connections,  and  auxiliary  ap- 
paratus. The  comparative 
costs  of  the  various  arrange- 
ments are  indicated  approxi- 
mately in  Table  I,  the  costs  given  covering  in  each  case  all  frame- 
work, (two  uprights)  or  concrete,  and  mountings  for  one  three-pole 
circuit-breaker  with  instrument  transformers,  etc.,  and  with  remote- 
control  mechanism;  in  other  words,  all  material  which  must  be  added 
to  the  self-contained  type  of  board  to  make  it  remote  controlled. 

It  should  be  remembered  that  wall  arrangements  such  as  shown 
in  Fig.  1,  may  be  more  costly  than  the  separate  arrangement  shown 
in  Fig.  2,  if  large  windows,  which  must  be  bridged  by  steel  work,  oc- 
cur back  of  the  board.  Concrete  or  masonry  structures  may  add  con- 


Fig.  4 — Combination  Wall  and  Framework 
Mounted  Structure 

For  heavy  current  capacity  at  low  voltage. 
Similar  to  arrangement  shown  in  Fig.  6.  In- 
expensive arrangement  of  control  mechanism. 
Space  back  of  board  entirely  free  from  main 
current-carrying  parts. 


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siderable  to  the  cost  of  floor  construction  and  support  on  account 
of  their  great  weight.  The  wall-mounting  arrangements,  shown  ip 
Figs.  1 and  8,  occupy  the  least  space  but  have  the  disadvantage  of 

Table  I. 

Wall  mounting  (Fig.  1)  including  I-beam  supports  for  remote- 

control  mechanism $ 8.00 

Separate  mounting  (Fig.  2)  including  I-beam  supports  for  re- 
mote-control mechanism 13.00 

Combination  wall  and  separate  mounting  (Fig.  4),  including 

slate  false  flooring  over  mechanism 10.50 

Combination  pipe  and  concrete  structure  (Fig.  9). $35.00  to  40.00 

Wall-supported  concrete  structure  (Fig.  8) 75.00  to  100.00 

Separate  concrete  structure  (Fig.  7) 75.00  to  100.00 


Fig.  5 — Large  Remote-Controlled  Switchboard 

With  apparatus  arranged  similar  to  Fig.  4.  Rheostats  mounted  in  view  of  operator 
above  the  board.  (Marathon  Paper  Company.) 

giving  accessibility  from  one  side  only.  For  this  reason  and  because 
of  the  great  increase  in  available  space  for  mounting  various  members 
of  the  assembly,  the  separate-mounted  structures  are  preferred  where 
space  can  be  found.  Fig.  4 shows  approximately  the  minimum  space 
which  is  required  for  the  average  structure,  while  more  generous  space 
is  provided  in  Fdg.  2.  All  high-tension  connections  and  circuit- 
breakers  in  Fig.  4 are  on  that  side  of  the  supporting  framework  away 
from  the  switchboard,  and  the  remote-control  mechanism  is  of  mini- 


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mum  length  and  weight.  Moreover,  if  desired,  a metal  screen  may 
be  placed  along  the  structural  uprights,  entirely  separating  the  low- 
tension  wiring  and- details  on  the  back  of  the  board  from  the  high- 
tension  apparatus,  thus  insuring  the  safety  of  attendants  when  work- 
ing at  the  back  of  the  switchboard. 

The  voltage  of  the  system  determines  the  spacing  of  the  vari- 
ous members  of  the  arrangement  and  influences  the  size  and  type 
of  the  circuit-breaker  chosen.  Moreover,  it  has  certain  influence 
on  the  arrangement  in  that  concrete  or  masonry  structures  are  not 
recommended  for  voltages  above  13200  volts.  This  recommenda- 


Fig.  6— End  View  of  Remote-Controlled  Switchboard 
Shown  in  Fig.  5 

False  flooring  over  control  mechanism  not  shown. 

enclosed  in  cells  if  desired,  as  shown  in  Fig.  1.  By  the  latter  is  meant 
those  circuit-breakers  assembled  from  unit  poles,  each  pole  being  de- 
signed to  occupy  a separate  cell,  as  shown  in  Fig.  10. 

The  current  capacity  of  the  individual  circuits  determines  the 
size  of  the  circuit-breaker,  and  the  nature  of  th^  connections  between 
circuit-breaker  and  bus-bars;  that  is,  whether  solid  wire,  copper 
rod,  copper  tubing,  or  copper  straps  must  be  used.  Moreover,  the 
current  capacity  determines  the  type  of  current  transformers.  Those 
shown  in  Figs.  1 and  2 are  for  small  current  capacity  and  require 


tion  is  due  to  the  fact 
that  for  higher  volt- 
a g e s,  concrete  or 
masonry  structures 
must  be  considered 
as  “dead  ground”  and 
therefore,  since  the 
tendency  toward 
leakage  and  corona 
increases  as  the  volt- 
age increases,  safe 
spacing  distances 
would  necessitate  a 
very  large  and  expen- 
sive structure. 

There  are  two  kinds 
of  circuit-breakers  as 
regards  their  mount- 
ing : those  designed  for 
wall  or  pipe-frame 
mounting  and  those 
forcellmounting.  Any 
of  the  former  may  be 


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special  mounting,  whereas  those  shown  in  Fig.  4,  for  large-current 
capacity,  are  designed  to  slip  over  the  laminated  strap  connections 
and  do  not  require  special  support. 

The  Remote-Control  Mechanism 

The  control  mechanism  which  is  used  to  the  practical  exclu- 
sion of  all  others  for  switches  and  circuit-breakers  consists  of  a 


Fig.  7 — Concrete  or  Masonry-Enclosed  Separate-Mounting  Structure 
Typical  arrangement  of  apparatus  and  bus-bars.  13200-volt  apparatus  shown. 
Self-supporting  and  accessible  from  both  sides.  May  be  entirely  enclosed  by  use  of  cell 
doors. 

Fig.  8 — Wall  Mounting  Concrete  or  Masonry  Enclosed  Structure 
13200-volt  apparatus  shown.  Requires  but  little  space.  Accessible  from  one  side 
only.  Provides  space  for  but  one  set  of  disconnecting  switches. 

Fig.  9 — Combination  Concrete  or  Masonry  and  Pipe  Framework  Structure; 
Self-Supporting 

Comparatively  inexpensive  construction,  is  of  less  width  than  arrangements  of  Figs. 
7 and  8,  but  live  parts  are  unprotected.  6600-volt  apparatus  shown. 


series  of  levers  and  rods.  The  direction  of  the  operating  force 
is  always  linear,  changes  in  direction  being  made  by  means  of  short 
levers  rotating  on  a fixed  fulcrum  commonly  known  as  “bell  cranks” 
(Figs.  1 1 and  12).  This  type  of  mechanism  lends  itself  readily  to  the 


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application  of  automatic  action,  especially  where  the  latch  and  trip 
coils  are  located  at  the  operating  handle.  The  connecting  rods  (Fig. 
11  and  12)  are  commonly  made  of  three-fourths  inch  gas  pipe,  as  it  is 
cheap  and  usually  easy  to  obtain,  and  is  naturally  well  suited  for  the 
purpose.  Wooden  rods  are  sometimes  used  because  of  their  light 
weight,  and  in  some  cases,  such  as  for  field  switches  or  disconnecting 
switches,  on  account  of  their  insulating  properties. 


Mechanisms  for  automatic  circuit-breakers  are  of  two  kinds; 
those  in  which  the  mechanism  is  stationary  during  automatic  trip- 
ping of  the  circuit-breaker,  in 
which  case  the  circuit-breaker  is 
said  to  trip  free  from  the  mech- 
anism, (Fig.  12),  and  those  in 
which  the  mechanism  returns  to 
the  open  position  (Fig.  11)  at 
the  time  of  opening  of  the  cir- 
cuit. The  latch  and  trip  coils 
may  be  mounted  at  the  circuit- 
breaker  for  both  kinds,  but  it  is 
most  usual  with  the  latter  kind 
to  mount  them  at  the  operating 
handle.  The  arrangement  of 
mounting  the  trip  coils  and  latch 
at  the  control  handle  with  the 
control  mechanism  and  breaker 
both  tripping  free  from  the 
handle  is  the  most  commonly 
used.  The  trip  coils  or  relays 
if  used,  are  usually  actuated  by 
the  same  current  transformers 
which  operate  the  ammeter,  and 
this  arrangement  permits  all  sec- 
ondary wiring  from  the  current 
transformers  to  be  made  at  the 
switchboard.  Moreover,  as  the  auxiliary  lever  (Fig.  11)  indicates 
the  open  or  closed  position  of  the  circuit-breaker,  the  operator 
does  not  require  a signal  device  at  the  switchboard  for  this  pur- 
pose. Where  the  distance  from  the  switchboard  to  the  circuit- 
breaker  is  considerable,  however,  it  is  advisable  to  place  the  trip 
coils,  latch,  and  relays,  if  used,  at  the  circuit-breaker  so  that  the 
latter  will  trip  free  from  the  heavy  mechanism.  In  this  case  an 
indicating  device  at  the  switchboard,  such  as  a lamp  or  mechani- 


Fig.  10 — Oil  Circuit-Breaker  Structure 
Corresponding  to  Fig.  8 

Showing  front  view  of  wall-mounting 
structure.  Two  complete  circuit-breaker 
units  shown.  (Used  by  Development  & 
Funding  Company.) 


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cal  signal,^ is  desirable  even  though  the  instruments  may  indicate, 
to  a certain  extent,  the  condition  of  the  circuit.  A long  heavy  mech- 
anism will  considerably  increase  the  inertia  of  the  moving  element 


Fig.  11 — Remote-Control  Mechanism  With  Latch  and  Trip  Coils  at  the  Handle 


Fig.  12 — Remote-Control  Mechanism  With  Latch  and  Trip  Coils  at  the  Circuit-Breaker 

The  mechanism  does  not  move  when  breaker  opens  automatically.  Automatic 
action  of  the  breaker  is  indicated  at  the  board  by  some  form  of  signal  device. 


Mechanism  moves  when  oil  circuit-breaker  opens,  the  auxiliary  handle  lever  tripping 
free  from  the  handle  while  the  main  handle  lever  remains  in  lower  position.  Mechanism 
shown  just  after  tripping. 


and  consequently  slow  down  the  action  of  the  circuit-breaker.  If, 
therefore,  this  form  of  mechanism  must  be  used,  an  accelerating  device 
such  as  a spring,  combined  with  a dashpot  to  absorb  the  shock  of 
opening,  should  be  applied  to  regain  the  inherent  speed  of  the  breaker. 


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Most  mechanisms  have  considerable  flexibility,  however,  owing 
to  the  manner  in  which  they  are  supported,  and  therefore  the  spring 
need  not  be  used  except  on  short  rigid  runs  of  mechanisms  and 
where  the  connection  is  made  direct  to  the  circuit-breaker  without 
the  use  of  bell  cranks. 


Fig.  13 — Substation  Arrangement  of  Switchboard 

Including  remote-control  high-tension  breaker,  bus-bars,  transformers,  lightning 
arresters,  choke  coils  and  disconnecting  switches. 


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V 

REMOTE  MECHANICALLY  - CONTROLLED 
SWITCHBOARDS— Continued 

By  C.  H.  SANDERSON 

\ 

Structure  Arrangements 

The  various  possible  arrangements  of  remote-controlled  switch- 
ing equipments  may  be  divided  into  two  classes  as  influenced  by  the 
system  of  connections  employed,  namely,  single  throw  and  double 
throw.  Either  of  these  classes  may  be  arranged  for  wall  mounting 
and  mayemploytheopen,  semi-enclosed,  or  entirely-enclosedstructure. 
Aside  from  the  inevitable  circuit-breakers,  bus-bars  and  connections, 
any  arrangement  under  consideration  may  be  influenced  materially 
by  the  presence  of  disconnecting  switches,  fuses,  and  instrument 
transformers  in  various  parts  of  the  circuit.  There  is  usually  much 
to  be  gained,  not  only  in  economy  of  cost  but  also  in  appearance, 
simplicity  and  ease  of  operation,  by  selecting  just  the  right  arrange- 
ment for  the  conditions  obtaining.  As  an  assistance,  therefore,  to  the 
proper  selection  of  apparatus  and  layout,  the  accompanying  illustra- 
tions are  presented.  While  the  usual  arrangements  are  fairly  covered 
it  is  quite  possible  that  the  best  arrangements  for  a particular  schedule 
of  apparatus  may  only  be  secured  by  combining  certain  desirable 
features  from  two  or  more  of  the  arrangements  illustrated. 

As  a further  assistance  in  deciding  upon  the  best  arrangement, 
it  may  be  said  that  small  stations  of  3000  k.v.a.  or  thereabouts 
are  hardly  justified  in  employing  any  other  than  the  open  arrange- 
ment, unless  local  rules  demand  that  the  apparatus  be  enclosed. 
Even  in  this  case  metal  grill  work  would  be  much  more  in  keeping 
and  much  less  expensive  than  cement  structures.  When  the  circuit- 
breakers  employed  are  of  the  type  having  one  supporting  frame  for  all 
poles,  and  it  is  considered  advisable,  because  of  the  frequent  heavy 
overloads  and  short-circuits,  to  enclose  the  circuit-breakers  in  cells, 
the  semi-enclosed  type  is  usually  chosen.  If,  under  the  same  con- 
ditions, the  current  capacity  is  large,  or  if  these  circuit  breakers  are 
of  cell-mounting  type,  it  is  usually  preferable  to  employ  the  com- 
pletely-enclosed arrangement. 

There  is  little  choice  between  the  horizontal  bus-bar  and  the 
vertical  bus-bar  arrangements  from  an  electrical  viewpoint,  as  per- 


1541 


Switchboards  For  Power  Stations 


73 


Fig.  37 — 2200  Volts  Two-Phase  Bus-Bar  Structure,  for  Ring  Bus 
as  illustrated  in  cross-section  in  Fig.  35 

cuits  at  some  other  part  of  the  system  or  from  something  falling 
against  or  upon  the  bus-bars  or  connections.  The  entirely-en- 
closed structure  is  the  only  real  insurance  against  excessive  in- 
jury to  the  equipment  in  case  of  arcing  grounds.  In  the  design 
of  the  enclosed  structure,  it  is,  however,  of  great  importance,  es- 
pecially when  the  higher  voltages  (11000,  13200,  etc.)  common 
to  structural  mounting  are  employed,  that  openings  at  different 
parts  of  the  structure,  which  might  create  a path  for  drafts,  be 
avoided.  For  the  lower  voltages,  especially  2200  volts  and  below. 


fectly  satisfactory  designs  may  be  obtained  from  either.  From  a 
mechanical  viewpoint  the  vertical  bus-bar  requires  greater  height 
and  less  width  but  practically  the  same  amount  of  supporting 
framework  and  the  same  length  of  connections.  It  is  obvious 
that  with  the  open-mounted  vertical  bus-bars,  the  danger  of  an  arc 
starting  at  some  point  on  one  of  the  lower  bus-bars  and  short- 
circuiting  the  upper  ones  is  greater  than  with  the  open  mounted 
horizontal  bus-bars.  An  arc  may  start  at  any  point  where  the 
insulation  to  ground  fails,  where  current-carrying  parts  of  oppo- 
site phase  or  different  voltage  are  too  close  together,  due  to  faulty 
erection,  to  accidental  displacement  of  the  members,  by  short-cir- 


74 


Switchboards  For  Power  Stations 


1541 


the  copper  connections  are  usually  very  heavy  and  of  large,  usually 
rectangular,  cross-section.  It  is  difficult  to  take  such  a connection 
through  a wall  without  considerable  expense  and  local  heating  of 
the  conductor,  except  by  means  of  an  opening  large  enough  to  give 
sufficient  insulation  of  air  around  the  conductor. 

While  the  enclosed  structure  has  many  advantages  for  in- 
stallations of  medium  voltage  and  current  capacity,  its  use  cannot 
be  justified  for  440  and  220-volt  installations.  The  danger  from 
arcing  is  here  negligible  and  the  matter  of  thorough  ventilation 
for  bus-bar  and  connections  is  of  prime  importance.  This  may  be 
appreciated  from  the  fact  that  the  heating  on  60-cycle  bus-bars 
of  heavy  capacity  is  approximately  twice  that  on  direct  current. 

When  choosing  an  arrangement  for  a double-throw  system, 
it  is  highly  recommended,  especially  for  stations  of  medium  or 
large  capacity,  say  3000  k.v.a.  and  above,  that  the  two  halves  of 
the  equipment  be  widely  separated  by  a fireproof  wall  if  possible. 
This  arrangement  both  minimizes  the  possibility  of  shut-down  and 
permits  safe  inspection,  or  work  to  be  done  on  the  idle  equipment. 

When  there  are  a considerable  number  of  circuits  to  be  con- 
trolled, necessitating  the  use  of  many  circuit-breakers,  it  is  neces- 
sary to  consider  carefully  the  location  of  the  switching  equipment 
in  regard  to  the  switchboard  panels.  The  angle  at  which  the  mechan- 
ism leaves  the  panel  is  of  no  consequence  except  as  it  causes  interfer- 
ence of  the  bell  cranks  and  their  supports  immediately  connecting 
to  the  control  handle.  The  length  of  the  mechanism  and  the  con- 
sequent weight,  however,  have  much  to  do  with  satisfactory  opera- 
tion. When  two^or  more  circuit-breakers  are  controlled  from  one 
panel  of  a large  board  it  may  be  necessary  even  to  form  the  structure 
in  a double  row,  back  to  back,  somewhat  as  shown  in  Figs.  4 and  5, 
with  the  bus-bars  in  the  shape  of  a U,  in  order  to  keep  the  mechanism 
more  nearly  at  right  angles  with  the  board,  thus  avoiding  interfer- 
ence of  the  bell  cranks. 

Costs 

Table  I gives  approximate  total  costs,  exclusive  of  installation, 
of  various  panels  with  complete  remote-control  arrangement  based 
on  the  panel  schedules  and  arrangements  shown  in  Figs.  1 to  36  in- 
clusive. The  panels  are  90  inches  high  with  framework  of  pipe  or 
angle  iron,  as  shown  in  the  corresponding  figures.  The  panel  ma- 
terial is  black  marine-finished  slate  2 inches  thick,  of  two  sections. 
All  apparatus  is  of  the  best  grade.  The  costs  includes  all  apparatus 
scheduled  in  Table  II,  and  everything  shown  in  the  figures  which  is 
not  a part  of  the  building  construction. 


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Switchboards  For  Power  Stations 


75 


Table  I — Approximate  Cost  of  Switchboard  Panels 


Fig. 

Cost 

♦U.B.C. 

Amps. 

Volts 

Kind  of  Panel 

Volts 

Amps. 

Fig. 

Cost 

*U.B.C. 

1 

$ 935 

15  500 

300 

6 600 

Generator 

2 200 

600 

19 

$ 480 

18  500 

1 015 

12  500 

300 

11  000 

6 600 

300 

500 

15  500 

1 

835 

15  500 

300 

6 600 

Feeder 

2 200 

600 

19 

420 

18  000 

855 

12  500 

300 

11  000 

6 600 

300 

390 

IS  500 

2 

360 

7 800 

300 

6 600 

Generator 

440 

600 

20 

340 

9 800 

305 

9 200 

300 

2 200 

440 

1 200 

390 

9 800 

2 

260 

7 800 

300 

6 600 

Feeder 

440 

600 

20 

290 

9 800 

255 

9 200 

300 

2 200 

440 

1 200 

340 

9 800 

3 

1 080 

15  500 

300 

6 600 

Generator 

2 200 

300 

" 21 

360 

9 200 

. 915 

12  500 

300 

11  000 

6 600 

300 

310 

7 800 

3 

860 

15  500 

300 

6 600 

Feeder 

2 200 

300 

21 

260 

9 200 

770 

12  500 

300 

11  000 

6 600 

300 

265 

7 800 

4 

340 

9 800 

600 

440 

Generator 

2 200 

300 

22 

375 

9 200 

385 

9 800 

1 200 

440 

6 600 

300 

325 

7 800 

4 

290 

9 800 

600 

440 

Feeder 

2 200 

300 

22 

280 

9 200 

335 

9 800 

1 200 

440 

6 600 

300 

285 

7 800 

6 

340 

9 800 

600 

440 

Generator 

440 

600 

24 

360 

9 800 

385 

9 800 

1 200 

440 

440 

1 200 

410 

9 800 

6 

285 

9 800 

600 

440 

Feeder 

440 

600 

24 

310 

9 800 

330 

9 800 

1 200 

440 

440 

1 200 

"355 

9 800 

7 

475 

18  000 

600 

2 200 

Generator 

6 600 

300 

25 

370 

7 800 

490 

15  500 

300 

6 600 

2 200 

300 

320 

9 200 

7 

410 

18  000 

600 

2 200 

Feeder 

6 600 

300 

25 

275 

7 800 

385 

15  500 

300 

6 600 

2 200 

300 

270 

9 200 

8 

350 

9 200 

300 

2 200 

Generator 

11  000 

300 

26 

695 

12  500 

295 

7 800 

300 

6 600 

6 600 

300 

590 

15  500 

8 

250 

9 200 

300 

2 200 

Feeder 

11  000 

300 

26 

560 

12  500 

255 

7 800 

300 

6 600 

6 600 

300 

505 

15  500 

9 

400 

9 200 

300 

2 200 

Generator 

2 200 

600 

27 

625 

18  000 

385 

7 800 

300 

6 600 

6 600 

300 

585 

15  500 

9 

360 

9 200 

300 

2 200 

Feeder 

2 200 

600 

27 

530 

18  000 

345 

7 800 

300 

6 600 

6 600 

300 

470 

15  500 

10 

400 

9 200 

300 

2 200 

Generator 

2 200 

300 

28 

270 

3 000 

375 

7 800 

300 

6 600 

2 200 

100 

240 

3 000 

10 

355 

9 200 

300 

2 200 

Feeder 

2 200 

300 

28 

230 

3 000 

345 

7 800 

300 

6 600 

2 200 

100 

212 

3 000 

11 

275 

3 000 

300 

2 200 

Generator 

2 200 

300 

29 

290 

3 000 

255 

3 000 

100 

2 200 

2 200 

100 

265 

3 000 

11 

215 

3 000 

300 

2 200 

Feeder 

2 200 

300 

29 

250 

3 000 

200 

3 000 

100 

2 200 

2 200 

100 

225 

3 000 

12 

440 

9 200 

300 

2 200 

Generator 

2 200 

300 

30 

425 

9 200 

385 

7 800 

300 

6 600 

6 600 

300 

375 

7 800 

12 

345 

9 200 

300 

; 2 200 

Feeder 

2 200 

300 

30 

330 

9 200 

350 

7 800 

300 

; 6 600 

6 600 

300 

325 

7 800 

13 

480 

9 200 

300 

2 200 

Generator 

2 200 

600 

31 

535 

18  000 

420 

7 800 

300 

6 600 

6 600 

300 

560 

15  500 

13 

410 

9 200 

300 

2 200 

Feeder 

2 200 

600 

31 

465 

18  000 

405 

7 800 

300 

6 600 

6 600 

300 

440 

15  500 

15 

550 

9 200 

300 

2 200 

Generator 

2 200 

600 

33 

780 

18  000 

445 

7 800 

300 

6 600 

6 600 

300 

800 

15  500 

IS 

415 

9 200 

300 

2 200 

Feeder 

2 200 

600 

33 

705 

18  000 

425 

7 800 

300 

6 600 

6 600 

300 

680 

15  500 

16 

700 

18  000 

600 

2 200 

Generator 

6 600 

300 

34 

490 

7 800 

640 

15  500 

300 

6 600 

2 200 

300 

435 

9 200 

16 

585 

18  000 

600 

i 2 200 

Feeder 

6 600 

300 

34 

410 

7 800 

515 

15  500 

300 

6 600 

2 200 

300 

405 

9 200 

17 

550 

7 800 

300 

6 600 

Generator 

6 600 

300 

35 

710 

7 800 

500 

9 200 

300 

2 200 

2 200 

300 

675 

9 200 

17 

475 

7 800 

300 

6 600 

Feeder 

6 600 

300 

35 

635 

7 800 

475 

9 200 

300 

2 200 

2 200 

300 

600 

9 200 

18 

915 

18  000 

300 

2 200 

Generator 

11  000 

300 

36 

1 240 

12  500 

1 

825 

15  500 

300 

6 600 

6 600 

300 

1 130 

15  500 

18 

800 

18  000 

300 

2 200 

Feeder 

11  000 

300 

36 

1 045 

12  500 

715 

15  500 

300 

6 600 

6 600 

300 

940 

15  500 

*The  column  marked  U.  B.  C.  gives  the  ultimate  circuit-breaking  capacity  of  circuit-breakers 
set  for  instantaneous  trip.  The  above  table  will  permit  of  obtaining  the  approximate  cost  of  a 
complete  switchboard.  The  cost  for  exciter  panels  may  be  taken  from  pages  34  and  44. 


76  Switchboards  For  Power  Stations  1541 


The  cuts  on  this  and  the  three  succeeding  pages  include  several  special  arrangements  which 
were  designed  to  meet  the  requirements  of  individual  installations.  Standard  arrangements  are 
applicable  for  most  installations  and  can  usually  be  adopted  to  good  advantage.  A few  typical 
standard  arrangements  are  shown  on  pages  81,  82  and  83. 


1541 


Switchboards  For  Power  Stations 


77 


78 


Switchboards  For  Power  Stations 


1541 


1541 


Switchboards  For  Power  Stations 


79 


Fig.  33 


Fig.  36 


Figs.  28  to  36 — Double  Bus,  Separate  Mounting  Arrangements 


80 


Switchboards  For  Power  Stations 


1541 


Table  II — Schedule  of  Apparatus  for  Standard  Panels 


Three-Phase  Generator  Panel,  16  Inches  Wide. 


1  Ammeter. 

1 Polyphase  indicating  wattmeter. 

1 Field  Ammeter. 

1 3-way  ammeter  switch. 

1 Synchronizing  receptacle. 

1 Voltmeter  receptacle,  8 pt. 

1 Field  switch. 

1 Rheostat  hand  wheel. 

1 Oil  circuit-breaker,  non-automatic  (single 

throw,  or  double  throw  by  means  of  one 
or  two  circuit-breakers  as  shown  in  Figs. 
1 to  36  inch). 

2 Current  transformers. 

2 Potential  transformers  with  fuses. 
Disconnecting  switches  when  shown. 


Three-Phase  Feeder  Panel,  16  Inches  Wide. 


1 Ammeter. 

1 Three-way  ammeter  switch. 

1 Oil  circuit-breaker — automatic  (single  throw 

or  double  throw  by  means  of  one  or  two 
breakers  as  shown  in  Figs.  1 to  36  inch). 

2 Relays;  single  phase,  overload,  inverse  time 

limit. 

3 Current  transformers. 

Disconnecting  switches  where  shown. 


Details 


It  is  of  importance 
to  the  appearance  of 
the  installation,  as  well 
as  to  its  fitness  as  a 
unit  in  the  electrical 
system,  that  all  details 
of  construction,  such  as 
supports  for  bus-bars, 
electrical  connections, 
operating  mechanisms, 
etc.,  be  uniform  in  de- 
sign throughout.  Fig. 
38  illustrates  many  of 
various  fittings  for  both 
pipe  and  angle  frame 
and  for  both  open  and  en- 
closed structures  which 
may  be  obtained  in  quan- 
tities from  any  large  sup- 
ply house.  In  designing 
a structure  the  arrange- 
ment of  parts  should  be 
madetoconform,asmuch 
as  possible,  to  the  ap- 
plication of  the  standard 


n 

Ln 

■■“'ll 

1 

w-|i 

ffl'! 

1 


f 


Fig.  38— Details  of  Switchboard  Construction 
for  Pipe  and  Angle  Frame  Work  and 
Masonry  Compartments 


1541 


Switchboards  For  Power  Stations 


81 


fittings  for  the  obvious  reason  that  the  first  cost  and  cost  of  spare 
parts  will  be  minimized,  and  that  advantage  is  thus  taken  of  the  ex- 
perience of  others  who  have  aided  in  the  standardizing  of  such 
fittings. 

Standard  Structure  Arrangements 

When  ordering  remote  control  switchboard  equipments,  it  is 
usually  possible  to  effect  a saving  in  time  of  delivery  and  in  cost, 
where  a station  is  laid  out  so  that  standard  structure  arrangements 
can  be  used.  The  Westinghouse  Electric  & Manufacturing  Com- 
pany has  standardized  various  structure  arrangements  which  are  ap- 
plicable to  most  installations. 

The  following  are  typical  standard  arrangements  listed  in  cata- 
logue section  DS1440  for  hand-operated  remote-control  oil  circuit- 
breakers. 


Fig.  39 — One  breaker  single-bus  without  disconnecting  switches. 
Fig.  40 — Two-breaker  double-bus  without  disconnecting  swicthes. 


Fig.  41 — One-breaker  single-bus  with  disconnecting  switches. 
Fig.  42 — One-breaker  double-bus  with  disconnecting  switches. 


82 


Switchboards  For  Power  Stations 


1541 


Fig.  43 — One-breaker  single-bus  with  disconnecting  switches  on 
each  side  of  breaker. 

Fig.  44 — Two-breaker  double-bus  with  disconnecting  switches 


Figs.  45,  46,  47,  48 — Various  wall-mounting  arrangements. 


1541 


■Switchboards  For  Power  Stations 


83 


Fig.  50 

Fig.  50 — Two- 
breaker  double- 
bus with  discon- 
necting switches 
(two-single  - bus 
structures). 


Fig.  49 

Fig.  49 — One-breaker  single-bus  with  disconnecting  switches. 


Fig.  51 


Fig.  51 — One-breaker  double-bus  with  disconnecting  switches. 


84 


Switchboards  For  Power  Stations 


1541 


' VI 

THE  ELECTRICALLY-OPERATED 
SWITCHBOARD 


By  C.  H.  SANDERSON 

The  electrically-operated  switchboard  usually  takes  one  of  three 
general  forms:  namely,  the  panel  board  (Figs.  2 and  3),  the  combi- 
nation control  desk  and  elevated  instrument  board,  (Figs.  4,  5 and 
7),  or  the  combination  pedestal  and  instrument  post  board  (Fig.  8). 

As  in  the  application  of  self-contained  or  remote  mechanically- 
controlled  switchboards,  there  is  no  well  defined  field  to  which  any 
of  the  three  forms  is  confined.  More  than  in  any  other  type  of 
switchboard  does  the  electrically-operated  board  approach  the  ideal 
of  the  designing  engineer,  as  it  is  almost  entirely  uninfluenced  by 


Fig.  1 — Various  Forms  of  Control  Switchboards  for  Electrically-Operated  Equipment 

the  form  of  apparatus  which  it  controls.  This  fact,  moreover, 
accounts  largely  for  the  great  variety  of  combinations,  some  of 
which  are  shown  in  Fig.  1. 

There  are,  however  certain  general  conditions  which  influence 
a choice  of  design  and  which  must  be  recognized  before  a satisfactory 
arrangement  can  be  obtained.  The  most  important  of  these  are: 


1 —  The  capacity  of  the  station. 

2 —  The  number  of  generator,  feeder,  bus-tie  and  exciter  circuits  to  be  con- 

trolled. 

3 —  The  relative  proportion  of  feeders  to  generator  circuits. 

4 —  The  scheme  of  bus-bars  and  inter-connections. 

5 —  The  location  and  arrangements  of  the  switchboard  gallery  as  regards  the 

location  and  arrangement  of  the  station  apparatus. 

6 —  The  first  cost  and  maintenance  cost. 

7 —  The  system  of  operation;  or,  the  usual  manner  in  which  the  various 

circuits  will  be  operated,  considered  together  with  the  provisional 
arrangements  for  emergency  use,  or  alternate  scheme  of  operation. 

8 —  The  number  and  kind  of  instruments  and  control  devices  to  be  used. 


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Switchboards  For  Power  Stations 


85 


Fig.  3 — Rear  View  of  Switchboard  Shown  in  Fig.  2 


86 


Switchboards  For  Power  Stations 


1541 


A discussion  of  the  various  forms  of  control  shown  in  Figs.  1 
to  8 will  illustrate  the  usual  methods  in  which  the  relation  of  the 
above  conditions  to  the  type  of  board  are  recognized. 

The  Panel  Board 

The  panel  board  is  the  least  expensive  and  the  simplest  in  con- 
struction. It  is  frequently  chosen  for  plants  of  moderate  capacity, 
and,  occasionally,  for  those  of  high  capacity  where  the  number  of 
circuits  are  few  and  the  length  of  the  board  is  therefore  kept  with- 
in a space  which  may  be  covered  almost  instantly  by  the  operator. 

The  panel  board  is 
invariably  chosen  for 
substations,  as  it 
must  generally  har- 
monize with,  and 
probably  be  an  ad- 
dition to  the  panel 
board  controlling  the 
low-tension  alternat- 
ing and  the  direct- 
current  circuits.  Oft- 
en the  control  for  the 
hand  - operated  and 
the  electrically-oper- 
ated apparatus  of  the 
substation  are  com- 
bined on  the  same 
panel,  thus  obtaining 
a small,  inexpensive 
and  simple  board. 

The  panel  board, 
although  the  simplest 
in  construction,  may, 
because  of  its  usually  great  length  where  applied  to  large  stations, 
be  much  more  difficult  to  operate  than  the  desk  control.  It  usu- 
ally requires  the  least  width  and  the  greatest  length  as  regards  floor 
space  and  is,  therefore,  sometimes  chosen  in  spite  of  other  possible 
disadvantages,  where  a long,  narrow  gallery  is  the  only  provision 
which  can  conveniently  be  made  for  the  switchboard.  The  open 
construction  of  wiring  and  control  busses,  as  obtained  by  use  of 
the  panel  board,  is  alone  responsible  for  its  adoption  by  many  en- 
gineers. 


1541 


Switchboards  For  Power  Stations 


87 


It  is  desirable  to  arrange  the  panels  to  correspond  with  the 
wiring  arrangement,  if  possible,  as  this  is  of  considerable  assistance 
to  the  operator  by  permitting  the  use  of  a dummy  or  miniature  bus, 
or  system  of  buses  on  the  front  of  the  panels,  thus  forming  a single 
line  diagram  of  the  complete  wiring  system.  The  conduit  system 
for  arranging  the  control  and  instrument  wiring  is  also  greatly  sim- 
plified. If,  however,  there  are  a great  many  circuits  to  be  con- 
trolled and  the  arrangement  is  such  that  a number  of  feeders  in- 
tervene between  each  generator  panel,  the  generator  panels  become 


Showing  arrangement  of  meter  receptacles  and  miniature  bus. 

too  widely  separated  to  be  under  the  immediate  supervision  of  the 
operator  and  must  be  assembled  at  one  end  or  at  the  center  of  the 
board  or  as  an  entirely  separate  board. 

The  Control  Desk 

The  combination  control  desk  and  elevated  instrument  board 
as  illustrated  in  Figs.  4 to  7 inclusive,  may  be  used  for  stations 
of  any  capacity  and  any  number  of  circuits.  The  particular  form 
chosen,  however,  must  depend  upon  the  local  conditions,  as  above 
described.  For  a small  number  of  circuits  the  linear  desk  (Figs. 
4 and  5)  may  be  employed,  while  for  a greater  number  of  circuits 


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the  semi-circular  desk  (Fig.  7)  is  more  desirable,  as  it  permits  a 
uniform  view  of  all  sections  of  the  desk  from  one  central  position. 

When  it  is  desired  to  use  a wall  of  the  building  for  support- 
ing the  instrument  panels,  the  arrangement  may  be  as  shown  in 
Fig.  1-b.  The  instrument  wiring,  except  for  a small  amount  beneath 
the  desk,  and  all  small,  unsightly  auxiliaries  may  thus  be’  located 
in  a separate  room. 

Where  there  are  a few  instruments  and  a very  compact  form 
of  desk  is  desired,  flush  type  instruments  inserted  in  the  top  of 


Fig.  6 Cross  Sectional  Drawing  of  Combination  Control  Desk  and  Elevated  Instrument 

Board 


For  generator  and  bus  tie  circuits,  with  double  semi-circle  feeder  board  of  the  panel 
type. 

the  desks,  as  in  Fig.  1-c,  or  standard  instruments  supported  above 
the  desk  as  in  Fig.  1-d,  may  be  used.  The  form  shown  in  Fig.  1-e 
is  the  next  step,  where  more  instruments  must  be  accommodated  on 
the  simplest  form  of  board.  In  this  form  also  the  desk  portion 
may  be  employed  for  generators  only,  while  the  feeders  are  accom- 
modated on  a continuation  of  the  instrument  section  extending 
to  the  floor  and  arranged  on  each  side  of  the  generator  sections. 
Fig.  1-f  may  be  employed  where  many  relays  and  other  auxiliaries 
must  also  be  accommodated.  With  this  arrangement  the  wiring  on 


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all  panels  may  be  entirely  enclosed,  at  the  same  time  making  it  very 
accessible.  When  it  is  considered  desirable  that  the  operator  have 
an  unobstructed  view  of  the  station  floor  while  standing  at  his 
board  in  the  gallery  the  forms  shown  in  1-g,  1-h,  1-i  or  1-j  may  be 


Fig.  7 — Circular  Type  Control  Desk 

Instrument  panels  supported  on  columns  which  form  part  of  the  desk  framework. 


adopted.  The  wiring  for  the  instruments  is  taken  up  through 
the  columns  supporting  the  instrument  panels,  which  are  covered 
at  the  back  with  expanded-metal  or  sheet-steel  removable  covers. 
The  instrument  columns.  Figs.  1-i,  or  1-1,  may  be  arranged  to  form 
a part  of  the  gallery  railing  where  desired. 


Fig.  8 — Combination  Pedestal,  Post,  and  Panel  Equipment 


When  the  number  of  feeder  circuits  is  very  large  as  compared 
to  the  number  of  generator  circuits,  a very  satisfactory  arrangement 
may  be  obtained  by  the  use  of  the  arrangement  shown  in  Figs.  1-j 


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and  1-k.  In  the  former,  the  switchboard  is  sometimes  built  in 
semi-circular  form,  where  there  is  a great  number  of  panels,  so  that 
all  meters  will  face  the  operator’s  desk.  The  arrangement  shown 
in  Fig.  1-k  may  be  used  when  it  is  desired  to  control  a great  number 
of  circuits  in  addition  to  the  generator  circuits  from  the  control  desk 
itself.  The  instruments  are  divided  between  the  front  and  rear 
switchboard , the  indicating  and  integrating  meters,  voltage  regulators, 
testing  receptacles,  etc.,  being  placed  on  the  front  board,  with  the 
relays,  relay  switches,  and  station  auxiliary  control  which  is  operated 
infrequently  on  the  rear  board.  The  ends  are  covered  with  grill 


Fig.  9 — Electrically-Operated  Double-Throw  Exciter  Board 

Containing  double-pole,  double-throw  switches  (panels  1,  3,  4 and  6)  for  four  exciters, 
and  double-pole,  double-throw  field  switches  (panels  2 and  5)  for  six  generator  fields. 

work,  provided  with  doors,  thus  forming  an  enclosed  compartment 
containing  the  more  unsightly  parts  of  the  board. 

Pedestals  and  Posts 

When  a station  is  equipped  with  very  large  units,  pedestals 
for  the  control  switches  and  receptacles,  with  posts  for  supporting 
the  instruments,  are  sometimes  used  because  of  the  complete  indi- 
viduality thus  obtained  for  each  unit.  The  chance  of  the  operator 
mistaking  the  wrong  control  switches  is  greatly  reduced  and  the 


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chance  of  trouble  in  the  small  wiring  communicating  itself  to  more 
than  one  unit  is  minimized.  This  form  of  control  may  be  used 
for  the  generators  only,  and  perhaps  for  the  transformer  banks 
when  used,  while  the  feeders,  which  require  less  attention,  are  pro- 
vided with  a panel  type  of  board. 


Fig.  10 — Rear  View  of  Exciter  Board  Shown  in  Fig.  9 


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VII 

CONTROL  EQUIPMENT  OF  THE  ELECTRICALLY 
OPERATED  SWITCHBOARD 

By  H.  A.  TRAVERS 

Control  desks  and  panel  boards  of  the  type  employed  for  large 
power  stations  contain  several  features  which  are  foreign  to  the  hand 
operated  boards.  While  some  of  these  could  be  applied  to  the  simpler 
switchboards,  if  desired,  questions  of  economy,  grade  of  switchboard 
operator  and  like  factors,  make  their  use  inadvisable.  In  the  case 
of  the  electrically-operated  board,  however,  controlling,  as  a rule 
large-capacity  generating  units,  transformers  and  feeders,  it  becomes 
desirable  and  essential  to  provide  refinements  to  the  switching  equip- 
ment such  that  the  station  attendant  may  operate  his  machines  to 
advantage,  know  exactly  what  he  is  doing,  and  act  quickly  and  cor- 
rectly and  prevent  mistakes  which  might  seriously  damage  large 
expensive  apparatus. 

The  Miniature  Bus 

For  the  proper  and  efficient  operation  of  an  electrically-operated 
panel  board  or  control  desk  of  any  size,  a miniature  bus  is  extremely 
desirable.  It  furnishes  the  operator  a bird’s  eye  view,  as  it  were,  of 
the  station  wiring,  since  the  miniature  bus  is  a skeleton  or  single-line 
diagram  of  all  main  circuits  of  the  station,  with  devices  for  indicating 
the  relative  location  of  all  circuit-breakers,  disconnecting  switches, 
generators,  power  transformers  and  feeder  circuits.  . The  miniature 
bus  is  usually  made  of  polished  copper  strap  run  along  the  top  of  the 
desk,  or,  in  case  of  a vertical  board,  on  the  face  of  the  panel. 

Fig.  1 shows  the  layout  of  the  miniature  bus-bar  of  a large  gen- 
erating station  controlling  eight  generators.  The  generators  have 
been  grouped  in  pairs  and  each  pair  of  generators  connects  to  a local 
bus;  from  there  to  a step-up  transformer  bank,  and  then  to  two  high- 
tension  feeders.  There  is  a common  low-tension  auxiliary  bus-bar 
to  which  all  the  generators  and  transformer  banks  may  be  connected 
if  desired,  so  as  to  permit  any  generator  of  one  group  feeding  a trans- 
former bank  in  another  group.  In  a similar  manner  there  is  a high- 
tension  tie  or  auxiliary  bus  which  permits  any  transformer  bank  to 
be  connected  to  any  group  of  outgoing  feeders. 

Attention  is  called  to  the  simple  manner  iirwhich  the  buses  have 
been  run  by  locating  the  generators  and  transformers  in  their  respec- 
tive groups,  rather  than  grouping  the  generators  at  one  end  of  the 
desk  and  feeders  at  the  other  end.  The  actual  location  of  the  circuit- 


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Fig.  2 — Semi-CirculariControl  Desk 


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breaker  corresponds,  of  course,  to  the  arrangement  indicated  by  the 
miniature  bus,  and  by  such  a layout  the  amount  of  current  to  be 
carried  by  any  section  of  the  bus  is  reduced  to  a minimum,  with  cor- 
responding decreased  cost  for  cables  from  generators  to  bus  struc- 
ture, etc.,  and  at  the  same  time  affording  great  flexibility  in  the  oper- 
ation of  the  system. 

For  stations  having  two  or  more  circuits  of  different  voltages 
such  as  2200  volts  for  generators,  11000  volts  for  local  feeders,  and 
44000  volts  or  higher  for  main  feeders,  it  sometimes  becomes  desir- 
able to  indicate  unmistakably  the  voltage  of  the  different  portions 
of  the  station  circuits.  This  is  readily  accomplished  by  giving  the 
respective  portions  of  the  miniature  bus  different  finishes,  such  as 
polished  copper,  mottled  oxide  copper,  nickel,  etc. 

Fig.  2 shows  another  station  in  which  the  generators  and  trans- 
former banks  are  grouped  at  one  end  of  the  desk  and  the  feeders  at 
the  other  end  of  the  desk.  Due  to  the  various  auxiliary  and  tie  bus- 
bars, it  is  noted  that  the  desk  is  largely  covered  by  numerous  minia- 
ture bus-bars. 

In  order  to  distinguish  between  the  different  miniature  buses 
on  this  particular  installation,  the  high-tension  and  low-tension  bus- 
bars were  made  in  different  colors.  The  low-tension  generator  bus 
was  finished  in  polished  nickel  and  is  shown  in  the  cut  by  plain  lines. 
The  neutral  bus  between  the  transformers  was  finished  in  mottled 
oxide  nickel;  this  is  shown  on  the  cut  by  hatched  lines.  The  main 
high-tension  bus-bars  were  finished  in  polished  copper  and  are  indi- 
cated by  a solid  black  line.  The  high-tension  relay  buses  were 
finished  in  mottled  oxide  copper  and  are  shown  in  solid  black  and 
white  lines. 

Had  it  not  been  for  the  different  finishes  on  these  miniature  buses 
a great  deal  of  confusion  would  have  probably  resulted  in  the  operation 
of  the  plant,  in  spite  of  the  fact  that  miniature  buses  were  placed 
on  the  desk  which  are,  of  course,  almost  an  actual  necessity,  in  order 
to  give  the  operator  any  indication  of  what  he  was  doing. 

The  relative  location  of  circuit-breakers  is  shown  by  placing 
either  the  dial  plate  and  handle  of  the  controller,  or  the  indicating 
lamp  (usually  red)  for  the  closed  position  of  the  breaker,  directly  in 
the  miniature  bus. 

Disconnecting  switches  are  indicated  in  several  ways. 

One  common  way,  which  is  the  height  of  simplicity  and  at  the 
same  time  rugged  and  reliable,  is  to  represent  the  dummy  disconnect- 
ing switch  by  a small  piece  of  metal  superimposed  on  the  top  of  the 
miniature  bus  in  its  proper  relative  location.  One  end  of  this  dummy 


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switch  is  hinged  to  a pair  of  phosphor-bronze  clips  that  are  bent 
toward  each  other  so  as  to  prevent  the  dummy  switch  from  bein'g 


turned  over  without  positive  ac- 
tion on  the  part  of  the  operator. 
One  side  of  the  dummy  switch  is 
given  a polished  copper  finish  the 
same  as  the  miniature  bus  and 
when  this  side  is  uppermost,  it  of 
course  indicates  that  the  actual 
disconnecting  switch  is  in  the 
closed  position.  The  other  side  of 
the  dummy  switch  is  given  a black 
finish  and  when  this  side  is  up- 
permost, an  apparent  '‘break”  has 
been  made  in  the  miniature  bus 
and  indicates  that  the  actual  dis- 
connecting switch  is  in  the  open 
position.  Fig.  3 shows  a drawl- 
ing of  this  switch. 


1-  ^ 

1 , 

l_ -jj..  J 

Fig.  3 — Dummy  Disconnecting  Switch 


Another  method  for  indicating  the  disconnecting  switches  is  to 
insert  small  telephone  switchboard  lamps  in  the  miniature  bus  and 
run  wires  to  snap  switches  located  near  each  set  of  disconnecting 
switches.  The  snap  switches  are  turned  to  the  corresponding  posi- 
tion of  the  disconnecting  switches  and  the  correct  indication  appears 
on  the  desk.  This  method,  while  more  expensive  on  account  of  the 
cost  of  control  wiring,  has  the  advantage  of  giving  more  reliable 
information  as  to  the  actual  position  of  the  disconnecting  switches, 
since  in  the  other  method  there  is  a possibility  that  the  operator  at  the 
control  desk  may  forget  to  set  the  dummy  disconnecting  switches 
in  the  proper  position;  or  a misunderstanding  may  arise  between  the 

desk  operator  and  the  attendant 
who  operates  the  disconnecting 
switches.  Fig.  4 indicates  how 
these  lamps  are  inserted  in  the  bus. 

The  location  of  a generator 
is  usually  indicated  by  means  of 
a card-holder  placed  at  the  end  of 
the  miniature  bus  strip  represent- 
ing the  connections  from  the  gene- 
rator. Power  transformersarein- 
dicated  by  breaking  the  miniature 
bus  and  placing  two  short  pieces 


Lens 


Fig.  4 


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at  right  angles  to  the  bus,  to  represent  the  high  and  low  tension  wind- 
ings of  the  transformer,  or  by  putting  card-holders  in  the  bus  at  right 
angles  to  it.  Feeder  circuits  are  either  sup- 
plied with  card-holders  at  the  end  of  the  strip 
of  miniature  bus,  thus  allowing  a card  to  be 
inserted  with  the  name  and  number  of  the  par- 
ticular feeder  circuit,  or  they  are  tipped  with 
an  arrow  head.  Sometimes  both  devices  are 
employed. 

Synchronizing  Devices 

Synchronizing  receptacles  are  placed  either 
directly  in  the  miniature  bus  at  a point  corres- 
ponding to  the  position  of  a circuit-breaker 
used  to  connect  a machine  or  incoming  feeder 
to  the  bus-bar,  or  else  convenient!}^  near  the  con- 
troller switch  of  the  synchronizing  circuit- 
breaker,  thus  affording  the  operator  visual  in- 

Fig.  5 — Synchronizing  Re-  , 

ceptacie  and  Plug  dicatiou  that  he  IS  usiug  the  proper  control 

switch  when  synchronizing.  The  synchroniz- 
ing schemes  usually  employed  with  control  desks  or  electrically- 
operated  panel  boards  are  of  such  a nature  as  to  interlock  the  closing 
circuit  of  the  circuit-breaker  through  an  extra  contact  on  the  syn- 
chronizing receptacle.  This  prevents  the  operator  from  closing  the 
circuit-breaker  without  first  inserting  the  synchronizing  plug  into  the 
proper  receptacle,  and  upon  so  doing  the  fact  is  brought  forcibly  to 
mind  that  the  particular  circuit  in  question  must  be  operating  syn- 
chronously with  the  bus-bars  before  attempting  to  close  the  circuit- 
breaker.  Fig.  5 shows  the  standard  type  of  synchronizing  receptacle 
and  plug  used  largely  where  machines  are  to  be  synchronized  to  a 
common  bus. 

Another  desirable  form  of  synchronizing  outfit  is  a rotary  drum 
type  receptacle  which  may  be  turned  to  the  right  or  left  by  means  of 
two  different  removable  keys  or  handles.  These  two  keys  are 
painted  different  colors,  usually  red  and  black,  one  known  as  the 
'‘incoming  key”  and  the  other  as  the  “running  key.”  Both  types  of 
receptacle  are  provided  with  contacts  for  synchroscope  and  also 
closing  coil  circuit  of  oil  breaker  if  desired. 

To  further  assist  operators  and  to  prevent  them  from  connecting 
together  circuits  that  have  not  been  properly  synchronized,  an  auto- 
matic synchronizer  may  be  used  to  excellent  advantage.  This  instru- 
ment is  essentially  a balancing  type  relay,  consisting  of  a walking 


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beam,  at  each  end  of  which  is  a solenoid.  Each  solenoid  has  two 
windings,  one  connected  to  a voltage  transformer  energized  from  the 
bus-bar  or  running  circuit 
and  the  other  connected 
to  a voltage  transformer 
energized  from  theincom- 
ing  circuit.  The  windings 
on  the  solenoids  are  so  re- 
lated that  only  when  the 
two  circuits  are  in  phase 
and  approximately  at 
synchronous  speeds,  will 
the  walking  beam  close  an 
auxiliary  contact,  which 
in  turn  completes  the  cir- 
cuit through  a suitable 
relay  switch  to  the  clos- 
ing coil  of  the  circuit- 

breaker  of  the  incoming  Fig.  6 — Automatic  Synchronizer 

machine.  Fig.  6 shows 

a front  view  of  this  device  and  Fig.  7 a diagram  for  same  in  connect- 
ing two  generator  circuit-breakers. 

The  particular  method  of  synchronizing  to  be  selected,  depends 
largely  upon  the  general  scheme  of  connections  involved.  In  sta- 
tions where  there  are  but  a few  machines  feeding  into  a single  or 
double  bus  that  is  not  sectionalized,  the  method  of  synchronizing 


A C Bus  Bars 


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each  machine  to  the  bus  generally  works  out  to  advantage.  Where 
the  bus  is  sectionalized  or  a ring  bus  is  employed,  the  method  of 
synchronizing  between  machines  usually  gives  better  satisfaction 
since  it  simplifies  the  synchronizing  wiring  and  reduces  to  a minimum 
the  number  of  voltage  transformers  required. 

Other  Electrically  Operated  Devices  for 
the  Control  Desk 

Besides  the  control  switches  for  the  electrically-operated  (gen- 
erator, feeder,  bus-tie  and  other)  circuit-breakers  that  may  be  re- 
quired, there  are  usually  several  other  electrically-operated  devices 
to  be  controlled  from  the  desk  or  board.  These  are  the  motor- 
operated  governor  for  the  prime  mover,  the  electrically-operated 
field-rheostat  face-plate,  the  electrically-operated  field  switch,  etc. 
In  hydro-electric  generating  stations,  controller  switches  for  opera- 
ting the  motor-driven  head-gates  on  the  penstock  are  often  added  at 
-the  desk.  As  a rule,  indicating  lamps  are  not  supplied  with  these 
control  switches.  However,  in  the  case  of  head-gate  motors  they  are 
sometimes  used  to  indicate  the  limits  of  travel  of  the  gate  or  the 
satisfactory  operation  of  the  motor.  The  control  switch  for  the 
head-gate  motors  is  usually  designed  so  that  when  thrown  to  posi- 
tion for  raising  the  head-gate  the  switch  must  be  held  by  the  operator 
during  the  operation.  This  prevents  the  gate  from  being  opened 
too  wide.  The  reverse  connection  however  can  be  made  and  left 
connected  by  the  operator,  the  motor  being  stopped  at  end  of  travel 
by  suitable  limit  switches  at  the  head-gate.  This  arrangement  is 
desirable  as  it  permits  the  operator  to  start  the  closing  of  head  gates 
in  case  of  trouble,  and  then  turn  his  attention  to  something  else  of 
prime  importance  that  is  usually  occurring  at  such  a time. 

The  governor-motor  control  switch  requires  no  lamps  since  the 
synchroscope  and  frequency  meter  give  indication  as  to  a change  in 
the  speed  of  the  prime  mover. 

Electrically  operated  rheostat  face-plates  occasionally  have  a 
lamp  to  indicate  a predetermined  position  for  the  rheostat  arm  after 
the  machine  has  been  running  and  the  fields  have  become  heated. 

Electrically  operated  field  switches  are  not  provided  with  indi- 
cating lamps,  as  the  field  ammeter  gives  an  indication  of  whether  the 
switch  is  opened  or  closed. 

Signal  Equipment 

With  the  present  tendency  toward  large  generating  units  and 
consequent  demand  for  careful  operation,  modern  electrically-oper- 


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ated  desks  and  boards  are  frequently  provided  with  a set  of  signaling 
devices  on  the  generator  sections,  whereby  the  switchboard  operator 
may  keep  in  close  touch  with  the  generator  room 
when  starting  up  and  connecting  in  an  idle  genera- 
tor or  when  shutting  down  a running  machine. 

These  signaling  devices  are  duplicated,  one  set 
being  at  the  control  desk  and  the  other  in  the 
engine  room  near  prime  mover.  The  outfit 
usually  consists  of  from  four  to  six  indicating 
lamps  with  flush  type  push-buttons  and  suitable 
legends,  either  on  the  lenses  of  the  lamps  or  on  the 
push-button  face  plate.  The  legends  commonly 
employed  are  ‘ ‘ Stand  by , ” “ Fast,  ” ' ‘ Slow,  ” “ Shut 
Down,  ” “O.K.,  ” “Transfer  Load,  ’’  and  the  like. 

There  should  also  be  an  additional  push-button  on 
the  desk  which,  when  held  closed,  will  cause  an 
electrically-operated  whistle  to  blow  or  gong  to  ring, 
thus  calling  the  attention  of  the  engineer  to  his 
signal  panel.  The  switchboard  operator  may  then 
instruct  the  engineer  to  start  up  a new  machine 
and  order  the  speed  raised  or  lowered  to  expedite  synchronizing,  the 
engineer  signaling  back  to  the  switchboard  as  soon  as  he  has  followed 
instructions.  Fig.  8 shows  a signal  pedestal  for  use  in  the  generator 
room.  Figs.  9A  and  9B  indicate  the  diagram  of  connections  for  such 
an  equipment  partly  shown  by  Fig.  8. 

Meter  Equipment 

The  selection  of  the  meter  equipment  becomes  of  more  impor- 
tance in  an  electrically-operated  system  than  on  the  small  boards,  for 
the  reason  that  many  more  economies  can  be  introduced  in  the  opera- 
tion of  a large  station  by  skilled  operators  with  a suitable  meter 
equipment,  than  would  be  possible  in  a smaller  plant.  At  the  same 
time  a multiplicity  of  meters  should  be  avoided  and  only  those  em- 
ployed which  will  give  most  quickly  the  information  desired.  Great 
assistance  in  determining  what  particular  kinds  of  meters  are  desired 
for  the  various  circuits  of  the  system,  may  be  derived  from  an  inspec- 
tion of  the  single-line  diagram  of  main  circuits  for  the  plant.  With 
such  a diagram  one  may  see  at  a glance  the  relative  importance  of 
one  circuit  to  another,  and  what  results  are  desired  from  the  gener- 
ators, transformers,  and  feeders.  A typical  single-line  diagram  is 
shown  in  Fig.  10,  with  a selection  of  instruments  indicated  for  each 
important  circuit.  For  each  generator  circuit,  one  ammeter  (with 


Fig.  8 


100  Switchboards  For  Power'  Stations  1541 


Fig.  9-A — Usual  Arrangement  Employed  for  Bell  Alarm  Circuits 


Fig.  9-B — Arrangement  with  Cieneral  Signal  on  Station  Wall  to  (^all  Engineer’s  Attention 

to  Particular  Machine 


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101 


three-way  ammeter  switch) , one  voltmeter,  one  indicating  wattmeter, 
one  field  ammeter,  and  one  power  factor  meter,  have  been  chosen. 
A bus  voltmeter  has  been  provided ; also  a frequency  meter  that  may 
be  plugged  either  to  the  bus-bars  or  to  any  machine.  Such  a meter 
equipment  will  give  all  the  desirable  and  useful  information  regarding 
the  operation  of  the  generators  that  may  be  required  in  a generating 


It  It 


Breakers  Shown\^\  are  Auto. 

For  reverse 
power  only. 

Breakers ShownX  I are  Non- Auto. 

Fig.  10 


plant  of  moderate  or  large  capacity.  In  a plant  of  such  size  the  load 
on  the  generators  is  usually  well  balanced  and,  consequently,  three 
ammeters  are  unnecessary.  By  means  of  a three-way  switch,  the 
one  ammeter  may  be  connected  in  on  any  of  the  three  phases  as  a 
check  on  the  loading  of  the  generator.  The  indicating  wattmeter 
gives  at  once  a direct  reading  of  the  power  output  of  the  generator, 


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and  the  power  factor  meter  will  give  instant  notice  whether  or  not 
the  operator  is  getting  the  most  out  of  the  generators  by  operating 
all  the  machines  at  the  same  power  factor.  The  field  ammeter  gives 
an  indication  of  heating  in  the  generator  field  and  is  especially  desir- 
able where  automatic  voltage  regulators  are  used.  In  such  cases  a 
higher  voltage  can  be  applied  across  the  field  windings  of  the  gener- 
ators, than  that  for  whicfi  they  are  designed  and  under  certain  con- 
ditions of  load  and  power  factor,  the  regulator  would  cause  the 
generators  to  become  unduly  loaded,  and  unless  the  field  ammeter 
is  used  as  well  as  the  indicating  wattmeter,  this  condition  might  not 
be  noticed  by  the  switchboard  operator. 

For  the  transformer  circuits  of  this  particular  station  it  is  found 
desirable  to  use  both  an  ammeter  and  indicating  wattmeter,  since 
the  transformer  bank  cannot  be  treated  as  a unit  with  the  generators. 
For  the  feeder  circuits,  three  ammeters  have  been  provided,  since  the 
ammeter  load  is  usually  the  determining  factor  and  a ground  on  one 
line,  unbalanced  loading,  etc.,  can  be  most  readily  noticed.  Watt- 
hour  meters  are  desirable  in  that  they  give  a record  of  the  power 
transmitted  over  each  feeder.  Other  indicating  meters  may  be 
added  if  conditions  warrant,  such  as  power  factor  meters,  compen- 
sated voltmeters,  and  the  like. 

Relay  Equipment 

This  portion  of  the  control  equipment  for  a large  power  station 
assumes  a degree  of  importance  not  usually  found  necessary  in  the 
small  capacity  stations.  With  large  amounts  of  power  concentrated 
at  one  locality  it  is  essential  that  suitable  and  reliable  relays  be  em- 
ployed to  safeguard  and  maintain  continuity  of  operation,  cutting 
off  from  the  system  such  apparatus  or  circuits  that  show  signs  of 
distress,  without  interfering  with  the  rest  of  the  system.  Consider- 
able development  in  the  last  few  years  has  now  brought  on  the  market 
a collection  of  relays  that  are  reliable  and  positive  in  operation, 
simple  in  design,  and  of  rugged  construction,  thus  affording  means 
of  protecting  any  system,  large  or  small.  No  attempt  will  be  made 
in  this  article  to  cover  the  design  features  of  the  various  relays  but 
rather  their  application  and  limitations. 

Referring  to  Fig.  10  it  will  be  noted  that  relay  equipments  as  well 
as  the  meters  have  been  indicated  for  the  various  circuits.  In  the 
generator  circuits  there  have  been  indicated  reverse-power  relays 
which  will  cut  off  a generator  from  the  bus-bar  in  case  of  an  internal 
short  circuit  or  other  source  of  trouble,  such  as  throwing  a dead 
machine  on  bus-bars  by  mistake,  which  would  cause  the  remaining 
generators  to  feed  into  the  one  in  trouble. 


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103 


Some  operators  also  favor  the  use  of  overload  relays  in  generator 
circuits  when  the  generator  is  being  synchronized  to  the  system, 

in  order  to  avoid  possible  trouble  due  to  a mistake  of  the  operator, 
throwing  the  generator  on  the  bus  when  the  incoming  machine  is  not 
in  synchronism  with  the  running  machines.  Of  course  the  generators 
that  are  running  should  not  have  the  overload  relays  connected  to 
the  tripping  coils  of  the  circuit-breaker.  The  temporary  relay  con- 
nection is  made  by  means  of  extra  contact  points  on  the  synchro- 
nizing receptacle  and  plug  so  that  only  when  the  plug  is  inserted  in 
the  receptacle  will  the  relay  trip-circuit  become  operative. 

In  some  cases  a single  overload  relay  is  connected  in  each  gener- 
ator circuit  with  its  tripping  circuit  connected  to  an  indicating  lamp 
on  the  control  desk,  or  an  alarm  bell,  or  both,  for  the  purpose  of 
warning  the  station  operator  that  the  generator  is  overloaded  and 
that  another  unit  must  be  put  into  service. 

For  protection  of  transformer  banks,  either  straight  overload 
inverse-time-limit  relays,  or  differentially  connected  overload  relays 
are  usually  employed.  If  the  former  are  used  the  design  of  the  relay 
should  be  such  that  it  can  be  set  so  as  to  trip  the  transformer  circuit- 
breaker  in  case  of  sustained  overload ; but  at  the  same  time  selective 
action  should  be  obtained  so  that  in  case  of  a short  circuit  on  one  of 
two  or  more  feeders  connected  to  the  transformer,  the  circuit-breaker 
of  the  defective  feeder  will  come  out  before  the  transformer  breaker, 
and  thereby  prevent  loss  of  power  on  the  remaining  feeders.  As  the 
bellows  type  of  inverse-time-limit  overload  relay  gives  practically 
instantaneous  action  under  short-circuit  conditions  it  is  obvious  that 
such  types  of  relays  are  not  suitable  and  the  induction  type  of  relay 
that  can  have  its  minimum  time  setting  adjusted  within  a range  of 
0.1  to  at  least  2 seconds  should  be  used.  This  type  of  relay  will 
give  the  familiar  inverse-time  action  of  the  bellows  type  of  relay 
down  to  one  or  two  seconds,  as  may  be  determined  by  proper  relay 
adjustment,  and  any  increase  of  current,  such  as  obtains  during  short- 
circuit  conditions,  will 
not  cause  the  relay  to  ^ 
trip  till  after  the  prede- 
termined  setting,  thus 
allowing  the  relays  in  the  |. 
feeder  circuit  to  act  first.  ^ . 

In  short,  this  relay  is  a § , 
combination  of  inverse- 

time  and  definite  - time  ^ wo  zoo  300  400  soo  600  too  800.  900  looo  /too  1200  m misoo 

1 T—  1 Percent  of  Norma!  Relay  Current  Setting. 

relays,  hig.  11  shows  ^ 


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the  typical  curves  for  the  straight  inverse  time-limit  relay  of  the  bel- 
lows-type,  and  the  induction  type  relay,  respectively.  Each  relay 
gives  the  inverse  time  element  feature  down  to  2 seconds  for  300  per 
cent  load  on  the  relay  for  a given  setting;  but  it  will  be  observed  that 
the  induction  relay  permits  greater  selective  action  since  the  curve  is 
not  so  steep  as  for  the  bellows  type.  Also  the  induction  relay  will  not 
become  instantaneous  at  500  per  cent  load  as  is  the  case  with  the 
bellows  type. 

As  indicated  in  Fig.  10  the  transformer  bank  for  this  station  has 
been  provided  with  instantaneous  differentially  connected  overload 
relays.  The  relays  are  inoperative  under  any  condition  of  load  so 
long  as  there  is  no  breakdown  in  the  transformer  itself,  since  the  relay 
is  connected  to  current  transformers  in  both  the  primary  and  second- 
ary side  of  the  power  transformer  banks,  the  connections  of  the  relays 
to  the  current  transformer  being  such  that  only  when  a difference 
exists  in  value  of  the  secondary  current  of  the  current  transformers 
will  the  relays  operate.  See  Fig.  12  for  diagram  of  connections  of 
current  transformers  and  relays.  Obviously  such  condition  cannot 


Fig.  12 — Connection  for  DiiTerentially  Connected  Instantaneous  Overload  Relays,  to 
Protect  Against  Break-Down  in  Transformer  Windings. 


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105 


obtain  unless  there  is  a breakdown  in  the  winding  of  the  power  trans- 
former. In  such  an  event  the  relays  operate  and  trip  out  the  circuit- 
breakers  on  both  sides  of  the  transformer  and  cut  it  off  from  the 
system. 

The  feeder  circuits  are  provided  with  straight  inverse-time-limit 
overload  relays.  These  may  be  either  of  bellows  or  induction  type, 
depending  upon  whether  minimum  time  eleriient  of  2 seconds  or  less 
is  required  under' short-circuit  conditions. 


Fig.  13— Relay  Equipment  to  Prevent  the  Circuit-Breakers 
from  Opening  in  Case  of  Grounds. 

In  stations  employing  duplicate  transmission  lines  and  having 
the  neutrals  on  high-tension  side  of  the  transformers  grounded 
through  a resistance,  it  is  often  desirable  to  provide  a special  relay 
equipment  for  maintaining  continuity  of  service  on  the  feeders. 
This  consists  of  a special  instantaneous  circuit-opening  relay  con- 
nected to  a current  transformer  in  the  neutral  ground  circuit  which 
will  operate  on  any  current  from  2 per  cent  to  full  load  of  the  trans- 
former bank.  In  case  of  a broken  wire,  arcing  ground,  etc.,  this 
relay  will  open  the  tripping  circuit  of  the  straight  overload  relays 
and  prevent  the  feeder  breaker  from  opening.  If  the  source  of 
trouble  continues  for  any  length  of  time  then  the  operator  has  time 
to  cut  in  the  parallel  feeder  and  manually  cut  out  the  defective 
feeder.  In  case  of  an  arcing  ground  which  usually  burns  itself  out, 
the  relay  will  automatically  restore  the  connections  of  the  overload 
relays.  In  event  of  a three-phase  short,  the  relay  in  the  neutral 


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Switchboards  For  Power  Stations 


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circuit  would  of  course  be  inoperative  and  the  overload  relays  would 
trip  out  the  feeder  breaker  at  once.  Fig.  13  shows  diagram  of  con- 
nections for  this  relay  equipment. 

The  relay  equipment  for  the  local  service  feeder  supplying  power 
to  the  exciter-motor-generator  set,  etc.,  has  been  equipped  with 
definite-time-limit  relays  in  order  to  prevent  this  breaker  coming  out 
due  to  a momentary  short  circuit  on  some  local  feeder  or  sudden  over- 
load such  as  starting  up  of  an  induction  motor.  It  is  apparent  that  the 
exciter  system  should  not  be  subject  to  interruption  unless  actual  dam- 
age to  the  exciters  would  result,  as  it  is,  of  course,  most  imperative  that 
the  generators  be  kept  excited  as  long  as  possible,  unless  abnormal 
conditions  exist. 

The  tie-bus  breakers  have  obviously  been  made  non-automatic, 
since  these  circuits  are  merely  “by-passes”  and  the  proper  protection 
has  already  been  provided  in  the  main  circuits.  In  some  installations 
tie-bus  breakers  are  inserted  in  the  main  bus-bars  between  groups  of 
generators  and  normally  short-circuit  bus-reactance  coils.  These 
breakers  are  then  made  very  quick  acting  and  are  provided  with 
instantaneous  direct-acting  trip  coils,  energized  from  current  trans- 
formers in  the  main  bus-bars.  Should  a short  circuit  occur  in  one 
section  of  the  bus-bar,  these  breakers  would  immediately  open  and 
cut-in  the  bus-reactance  which  will  prevent  the  generators  on  the 
other  sections  of  the  bus  from  feeding  into  the  short  circuit  and  also 
prevent  loss  of  voltage  on  the  feeders  connected  to  the  sections  of  the 
bus-bar  not  in  distress. 


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VIII 

CIRCUIT-BREAKER  STRUCTURE  ARRANGE- 
MENTS FOR  ELECTRICALLY-OPERATED 
STATIONS 

By  H.  A.  TRAVERS 

As  indicated  in  the  first  few  paragraphs  of  these  papers  the 
electrically-operated  board  is  usually  employed  for  stations  of  large 
capacity  requiring  heavy  breakers  not  easily  closed  by  hand,  or  where 
the  design  of  the  station  is  such  that  hand-operated  remote-control 
breakers  cannot  be  used  to  advantage  due  to  the  excessive  lengths 
of  operating  rods  required. 

All  the  advantages  gained  by  the  use  of  hand-operated  remote- 
mechanical-control  breakers  over  switchboard-mounting:  breakers 
are  applicable  to  the  electrically-operated  breaker  installations.  As 
stated  under  discussion  of  the  remote-hand-operated  boards,  the 
space  required  for  breakers  and  bus-bars  for  a given  capacity  will  be 
practically  identical,  but  due  to  the  absence  of  operating  rods,  bell 
cranks,  etc.,  arrangements  and  designs  of  structures  can  be  used  that 
are  not  possible  otherwise  and  that  present  various  adaptations  to 
certain  desirable  building  designs,  which  are  out  of  the  question  with 
hand-operated  remote-control  breakers.  This  is  particularly  evident 
in  large  stations  where  high-tension  voltages  such  as  2400,  6600  and 
11000  are  used  for  generators,  and  where  extra  high-tension  voltages 
such  as  22000,  44000,  66000,  etc.,  up  to  150000  are  employed  for 
distributing  circuits.  The  variety  of  structure  arrangements  with 
electrically-operated  circuit-breakers  is  almost  unlimited,  but  good 
operating  practice  has  evolved  certain  typical  designs  which  are 
illustrated  in  the  following  cuts  and  a brief  discussion  will  be  given 
for  each  arrangement  shown. 

In  general  it  may  be  stated  that  there  are  six  general  types  of 
structure  arrangements  in  use. 

(1)  Wall  mounting — All  apparatus  and  bus-bars  either  mount- 
ed directly  on  or  supported  from  a wall  of  the  building. 

(2)  Frame  work  mounting — all  apparatus  and  bus-bars  mount- 
ed on  a framework  of  iron  pipe  or  structure  steel  shapes. 

(3)  Combination  wall  or  framework  mounting. 

(4)  Concrete  or  masonry  structure  mounting — all  apparatus 
mounted  in  cells. 

(5)  Combination  concrete  and  structural  mounting — circuit- 
breaker  in  cells,  with  bus-bars,  etc.,  on  iron  framework. 


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(6)  Floor  mounting  and  structural  mounting — circuit-breakers 
set  on  floor,  with  bus-bars,  etc.,  mounted  on  iron  framework. 

It  will  be  noted  that  the  first  five  general  types  of  structure 
arrangements  are  parallel  to  those  mentioned  in  the  article  on  re- 
mote-mechanical-control switchboards.  The  sixth  arrangement  ap- 
plies particularly  to  high  voltage  layouts  of  22000  volts  and  above, 
using  the  floor-mounting  type  of  circuit-breaker. 

The  same  reasons  for  selecting  a given  type  of  structure  should 
be  observed  as  have  been  outlined  under  the  hand-operated  remote- 
mechanical-control  switchboards.  The  factors  involved  are  identical. 
The  following  illustrations  show  the  use  of  the  solenoid-operated 
circuit-breakers  entirely,  and  have  not  considered  motor-operated 
breakers.  It  will  be  noted  that  breakers  of  relatively  small  ultimate 
k.v.a.  breaking  capacity  and  of  voltages  up  to  13200  and  having  a 


single  frame  for  all  poles  with  a single  tank,  have  the  solenoid  mech- 
anisms fastened  directly  to  the  frame  of  the  circuit-breaker.  This 
makes  the  breaker  a more  or  less  self-contained  unit.  The  remaining 
breakers  which  are  built  with  each  pole  a separate  unit  with  its  own 
frame  and  tank  are  operated  from  one  solenoid  acting  on  a common 
operating  mechanism  to  which  each  pole  is  connected. 

Figs.  1 to  4 show  typical  structures  both  for  single-throw  and 
double-throw  bus  systems,  with  disconnecting  switches  either  on  one 
side  of  the  breaker  or  on  both  sides,  for  installations  for  voltages  up 
to  6600  and  of  relatively  small  capacity.  As  will  be  noted  these 
breakers  have  the  self-contained  solenoid  mechanism  as  part  of  the 
circuit-breaker  framework.  Fig.  1 shows  a one-breaker  single-bus 
structure  with  disconnecting  switches  between  the  bus  and  the 
breakers.  Fig.  2 shows  the  one-breaker  double-bus  structure  with 


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disconnecting  switches  between  the  bus  and  breaker.  Fig.  3 shows 
a one-breaker  single-bus  structure  with  disconnecting  switches  on 
either  side  of  the  breaker.  Fig.  4 shows  a two-breaker  double-bus 
structure  with  disconnecting  switches  on  either  side  of  the  breaker. 


Figs.  7-8 


Fig.  7 


Fig.  8 


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Figs.  5 to  8 show  the  next  size  frame  breaker  which  has  all  poles 
in  one  frame  but  separate  tanks  for  each  pole.  This  breaker,  being 
heavier,  makes  it  desirable  to  have  the  solenoid  mechanisms  remote 
from  the  breaker,  as  shown.  This  type  of  breaker  can  be  used  with 
voltages  as  high  as  22000  where  the  total  station  capacity  is  small 
enough  so  as  not  to  require  the  use  of  a cell  structure  for  the  breakers. 
The  structure  shown  in  the  cut  is  limited  to  13200  volts  however. 


Figs.  9 to  12  show  the  open  type  of  structure  similar  to  the  pre- 
vious figures  and  the  same  voltage  class  of  service  as  indicated  for 
Figs.  5,  6,  7 and  8.  The  essential  difference  in  this  structure  being, 
of  course,  the  use  of  breakers  having  a separate  frame  and  tank  for 
each  pole  with  all  poles  operated  from  a single  solenoid  by  means  of  a 
suitable  countershaft.  While  the  breakers  shown  in  these  figures 
are  suitable  for  voltages  up  to  22()()(),  depending  upon  the  ampere 
capacity,  it  is  the  intention  with  this  arrangement  of  structures  to 
limit  the  operating  voltage  to  13200  volts,  as  has  been  indicated  by 


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the  type  of  disconnecting  switch  and  current  transformer  shown. 
The  use  of  a breaker  suitable  for  a much  higher  voltage  than  the 
operating  voltage  is  very  often  resorted  to  in  order  to  obtain  suffi- 
cient breaking  capacity  on  account  of  the  total  installed  k.v.a.  of 
synchronous  machines.  As  stated  in  the  first  article,  the  ultimate 
k.v.a.  breaking  capacity  of  a given  circuit-breaker  may  be  increased 
approximately  1 per  cent  for  every  1 per  cent  decrease  in  voltage 
from  the  rated  voltage  on  the  breaker. 


Fig.  15 


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Fig.  16 


Figs.  13  to  16  illustrate  the  use  of  the  same  breakers  as  have  been 
shown  previously  except  that  they  are  mounted  on  the  side  of  the 
station  wall  and  may,  if  desired,  be  enclosed  by  cells  of  concrete, 
soapstone,  asbestos  lumber,  or  other  suitable  material.  Figs.  13  and 
14  show  the  small  type  of  breaker  with  self-contained  solenoid 
mechanisms  for  either  single  or  double  bus-bars  with  disconnecting 
switches  between  the  breaker  and  the  bus.  Fig.  15  shows  the  two- 
breaker  double-bus  structure,  with  one  breaker  and  bus  mounted  on 
either  side  of  the  wall.  Fig.  16  shows  the  larger  frame  breaker, 
having  separate  tank  and  frame  for  each  pole,  with  the  bus-bars 
attached  to  braces  fastened  to  the  wall  and  the  breaker  mounted  on 
a suitable  pipe  framework  very  close  to  the  wall.  If  this  breaker  is 
to  be  enclosed  in  a cell  structure  a slightly  modified  form  is  used  as 
shown  in  Fig.  17. 


rig.  17 


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Figs.  18  and  20  show  the  concrete  or  masonry  type  of  structure 
using  the  small  circuit-breakers  which  have  a single  frame  for  all 
three  poles,  with  either  the  self-contained  solenoid  mechanism  as  per 
Fig.  18  or  the  separate  solenoid  mechanism  as 
shown  in  Fig.  20.  If  desired  the  three  poles  of 
the  smaller  sizes  of  the  individual-pole  breakers 
may  be  mounted  in  a single  cell  similar  to  the 
figures,  in  which  case  the  breakers  would  be 
mounted  on  the  rear  wall  of  the  structure  in  order 
that  the  total  depth,  dimension  C,  would  remain 
the  same.  Of  course  dimension  D,  the  width  of 
the  cell  structure,  would  be  increased  somewhat. 

It  is  usually  the  practice,  however,  to  use  sepa- 
rate cell  compartments  for  each  pole  when  this  type  of  breaker  is 
used,  as  illustrated  in  the  following  figures.  Fig.  18  shows  a one- 
breaker  single-bus  structure  with  disconnecting  switches  on  either 
side  of  the  breaker.  Fig.  19  shows  the  arrangement  for  a two- 
breaker  double-bus  structure.  It  will  be  noted  that  the  current 
transformer  is  to  be  located  underneath  the  floor  at  the  point  where 
the  tie  connection  between  the  two  breakers  has  been  made.  Fig. 
20  shows  a one-breaker  double-bus  structure  with  disconnecting 
switches  on  either  side  of  the  breaker. 

Figs.  21  to  24  have  been  shown  to  indicate  the  adaptability  of 
the  solenoid-operated  circuit-breakers  of  different  sizes  and  capacity 
to  the  same  type  of  circuit-breaker  structure.  Fig.  21  indicates  the 
type  of  breaker  having  the  single  frame  with  either  a common  tank 
for  all  poles  or  a separate  tank  for  each  pole,  with  the  solenoid  mechan- 


1541 


114 


Switchboards  For  Power  Stations 


ism  placed  above  the  breaker.  These  breakers  belong  to  the  first 
two  classes  on  page  13  in  the  first  article.  Fig.  22  shows  the  heavy 
capacity  type  of  breaker  designed  particularly  for  cell  mounting  with 
a single  frame  or  base  for  the  operating  mechanism.  These  breakers 
are  for  voltages  from  2200  to  22000  and  have  a k.v.a.  breaking  capac- 
ity ranging  from  35000  to  70000.  Fig.  23  shows  a smaller  type  of  cell 
mounting  breaker  and  has  a breaking  capacity  ranging  from  16000  to 
40000  k.v.a.  Fig.  24  shows  one  of  the  heaviest  breaking  capacity 
breakers  on  the  market  of  the  cell  type.  This  breaker  has  a breaking 
capacity  of  80000  to  100000  k.v.a.  and  an  ampere  capacity  of  600  to 
4000  amperes.  As  may  be  noted  these  four  different  types  of  breaker 
can  l)e  placed  in  the  same  structure  without  any  change  in  the  struc- 
ture design,  and  this  feature  becomes  particularly  dcvsirablc  in  many 


1541 


Switchboards  For  Power  Stations 


115 


cases  where,  by  means  of  suitable  relays  in  connection  with  the 
breakers,  a somewhat  smaller  or  less  expensive  breaker  may  be  used 
on  certain  circuits  of  the  system,  such  as  generators  where  the 
breakers  are  usually  non-automatic;  whereas  in  the  case  of  the 
feeders  having  automatic  breakers,  a heavier  breaker  is  necessary  on 
account  of  it’s  having  to  open  under  a short  circuit. 

Figs.  25  to  27  show  the  various  combinations  possible,  using 
the  type  of  circuit-breaker  structure  illustrated  by  Figs.  21,  22,  23, 
and  24,  any  of  these  breakers  being  adapted  to  the  arrangement 
shown  in  these  outlines.  Each  cut  shows  anywhere  from  four  to 


116 


Switchboards  For  Power  Stations 


1541 


Fig.  26 


six  different  arrangements  as  indicated  by  the  letters  A,  B,  C,  D,  E 
and  F,  the  arrows  emanating  from  these  letters  showing  just  what 
is  included  under  that  sub-arrangement.  Fig.  25-A  shows  a one- 
breaker  single-bus  structure  with  all  main  leads  from  below;  hig. 
25-B  shows  a two-breaker  double-bus  structure  with  all  main  leads 
from  below.  With  such  an  arrangement  the  leads  from  both  breakers 
will  be  tied  together  underneath  the  floor  at  the  points  indicated  by 
the  horizontal  dotted  connections.  Fig.  25-C  is  a one-breaker  single- 


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Switchboards  For  Power  Stations 


117 


bus  structure  with  all  main 
leads  from  above ; Fig.  25-D  is  a 
two-breaker  double-bus  struc- 
ture with  all  main  leads  from 
above, the  tieconnectionsbeing 
indicated  by  the  dotted  hori- 
zontal connections  directly  un- 
derneath the  second  floor.  Fig. 
25-E  is  a two-breaker  double- 
bus  structure  with  the  struc- 
tures arranged  one  above  the 
other  on  separate  floors,  all 
main  leads  leaving  from  the  tie 
connections  between  the  tw'o 
structures.  It  will  be  noted  that 
this  arrangement  is  a combina- 
tion of‘A”and‘ ‘C.”  Fig.25-F 
is  a one-breaker  single-bus 
structure,  with  two  rows  of  cir- 
cuit-breakers arranged  one  on 
either  floor.  The  leads  would 
leave  from  below  on  the  upper 
floor,  and  from  above  on  the 
lower  floor.  A duplicate  struc- 
ture has  been  indicated  in 
dotted  lines  and  may  be  used 
for  a two-breaker  double-bus 
system. 

Fig.  26-A  is  a one-breaker  single-bus  structure  with  all  main 
leads  from  below,  having  the  bus-bars  and  voltage  transformers 
on  the  upper  floor  and  the  circuit-breaker  with  the  disconnecting 
switches  on  the  lower  floor.  Fig.  26-B  is  a two-breaker  double-bus 
structure  same  as  indicated  for  the  “A”  arrangement.  Fig.  26-C  is 
a one-breaker  single-bus  structure  with  all  main  leads  from  above, 
the  breaker  with  the  disconnecting  switches  being  on  the  second 
floor  and  the  bus-bars  and  voltage  transformers  on  the  ground  floor. 
Fig.  26-D  is  a two-breaker  double-bus  structure  corresponding  to  the 
single-bus  structure.  Fig.  26-E  is  a two-breaker  double-bus  struc- 
ture using  four  floors,  instead  of  two  as  mentioned  above  for  the 
“D”  arrangement. 

Fig.  27-A  shows  a bus  compartment  on  the  floor  above  the  cir- 
cuit-breaker structure,  with  all  main  leads  from  below.  Fig.  27-B 


Fig.  27 


118 


Switchboards  For  Power  Stations 


1541 


Fig.  28 


shows.thebuscompartmenton  the 
floor  below  the  breaker  with  all 
main  leads  from  above.  In  the 
“B”  arrangement  note  that  the 
disconnecting  switches  and  the 
voltage  transformers  in  the  bus 
compartment  structure  would  be 
interchanged  in  position.  Fig. 
2 7-C  shows  a two-breaker  double- 
bus structure  with  the  bus  com- 
partment on  the  floor  between  two 
rows  of  breakers ; one  row  of  break- 
ers is  on  the  first  floor  and  the  other  on  the  third  floor.  The  breakers  on 
the  first  floor  have  the  leads  come  from  below  and  the  breakers  on  the 
third  floor  have  the  leads  come  from  above.  The  voltage  trans- 
formers in  the  bus  structure  would  be  replaced  by  disconnecting 
switches  for  use  with  the  top  row  of  circuit-breakers.  Fig.  27-D 
shows  the  bus  compartment  on  the  same  floor  as  the  breakers.  The 

leads  may  be  from  above  or  below  as  de- 
sired according  to  the  location  of  the  dis- 
connecting switches  and  the  connections 
from  the  breaker  to  the  bus.  In  the  illus- 
tration the  disconnecting  switches  are 
shown  at  the  top,  which  would  indicate 
that  the  leads  to  the  breaker  would  come 
from  below.  The  voltage  transformers 
may  be  placed  underneath  the  bus  com- 
partments where  space  is  available, 
although  they  are  not  shown. 

Fig.  28  shows  a typical  layout  for  cir- 
cuit-breaker and  bus  structure  for  22000 
volts  using  the  pipe-frame-mounting 
type  of  circuit-breaker.  This  arrange- 
ment shows  a single-bus  system  with  the 
outgoing  line  breakers  in  one  row  having 
disconnecting  switches  on  either  side  of 
the  line  breakers,  and  transformer  break- 
ers in  the  other  row  with  disconnecting 
switches  between  the  bus  and  breaker 
only. 

Figs.  29  to  33  show  various  arrange- 
ments of  floor  mounting  circuit-breakers 


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Switchboards  For  Power  Stations 


119 


Fig.  32 


Fig.  31 


120 


Switchboards  For  Power  Stations 


1541 


for  high-tension  structures  of  22000  volts  and  upward.  Fig.  29  shows 
an  arrangement  for  a one-breaker  single-bus  system  with  disconnect- 
ing switches  on  either  side  of  the  breaker,  if  desired,  when  a long 
rectangular  space  is  available.  Fig.  30  shows  an  arrangement  for  a 
one-breaker  single-bus  layout  where  a wider  space  is  available  and 
thereby  cuts  down  the  total  length  of  the  high-tension  room  by  plac- 
ing the  breakers  in  two  rows.  Fig.  31  shows  an  arrangement  for  a 
one-breaker  double-bus  system.  Fig.  32  shows  a two-breaker  double- 


bus system  suitable  for  use  with  a long  narrow  room.  Fig.  33  shows 
an  arrangement  for  a two-breaker  double-bus  system  where  a wider 
and  shorter  room  is  available. 

Figs.  34  to  36  show  typical  switching  bays  of  power  stations  with 
high-tension  power  transmission.  Fig.  34  is  a layout  which  is  very 
common  to  water  power  plants  where  a long  narrow  space  is  avail- 
able. This,  of  course,  is  the  usual  layout  for  hydro-electric  power 
stations.  The  transformer  bays  are  arranged  with  openings  into  the 


1541 


Sii'itchboards  For  Power  Stations 


121 


generator  room  to  permit  rolling 
out  the  transformer  in  case  repairs 
are  necessary.  Fig.  35  is  another 
modification  of  this  layout  with 
the  low-tension  breaker  structure 
on  the  same  floor  with  the  trans- 
formers. This  arrangement,  as 
will  be  noted,  obviates  the  use  of 
an  addition  to  the  power  house 
for  the  high-tension  room. 

Both  Figs.  34  and  35  indicate 
the  use  of  a two-breaker  double- 
bus system  on  the  low- tension  side 
and  a two-breaker  double-bus  Fis-  34 

system  on  the  high-tension  side. 

In  Fig.  35  the  power  transformers  are  to  be  removed  through  the 
generator  room.  The  same  was  indicated  in  Fig.  34. 

Fig.  36  shows  a still  different  arrangement  of  the  same  layout 
where  a wider  building  is  available  and,  in  this  case,  it  will  be  noted 
that  the  low-tension  circuit-breaker  structure  has  been  divided  and 
one  bus  with  its  breakers  located  on  the  upper  floor,  with  the  second 
bus  and  breakers  on  the  lower  floor.  In  this  case  the  power  trans- 
former banks  are  removed  directly  to  the  outside  of  the  building  on  a 
track  as  indicated.  Such  an  arrangement  is  extremely  desirable 
where  the  ground  space  is  available,  as  it  lessens  the  cost  of  the  power 
station,  since,  if  it  is  necessary  to  remove  the  power  transformers 


Fig.  35 


Fig.  36 


122 


Switchboards  For  Power  Stations 


1541 


through  the  generator  room,  necessarily  waste  space  has  to  be  roofed 
which  otherwise  can  be  eliminated. 

While  it  would  be  possible  to  give  a great  many  other  different 
arrangements,  they  all  more  or  less  are  based  upon  the  layout  shown 
in  the  above  cuts.  Consequently,  it  would  not  be  of  material  value 
in  an  article  of  this  nature  which  must  necessarily  cover  the  general 
features  of  design  whereas  each  particular  station  requires  individual 
treatment. 

In  connection  with  the  last  three  layouts,  it  will  be  noted  that  the 
lightning-arrester  equipments  have  not  been  shown.  It  usually 
works  out  to  advantage  to  either  place  these  arresters  on  the  ground 
alongside  of  the  building  or  mount  them  on  the  roof  of  the  high- 
tension  room  in  a convenient  location  to  the  roof  outlet  bushings. 
Where  weather  conditions  will  permit,  it  is  recommended  that  the 
entire  arrester  be  placed  out  of  doors,  as  this  obviously  saves  a con- 
siderable amount  of  floor  space.  However,  where  temperatures  of 
— 15  degrees  Centigrade  are  apt  to  exist  for  any  length  of  time,  the 
arrester  tank  may  be  placed  indoors  but  the  horn  gaps  can  still  be 
left  outside.  Such  an  arrangement,  of  course,  means  the  use  of  three 
additional  roof  outlet  bushings  in  case  of  a three-phase  system  or 
four  in  the  case  of  a two-phase  system;  but,  as  a rule,  the  extra  cost 
of  these  roof  outlet  bushings  is  considerably  less  than  would  be  the 
cost  for  the  larger  building  necessary  to  provide  sufficient  space  above 
the  horn  gaps  of  the  arresters  in  case  they  were  placed  inside  the 
building. 


1541 


Switchboards  For  Power  Stations 


123 


SOME  EXAMPLES  OF  WESTINGHOUSE  CIRCUIT- 
BREAKERS  AND  SWITCHBOARDS 


Type  F-1  Oil  Circuit-Breakers.  Three-Pole  Single-Throw 
300-Ampere  4500-Volt,  Panel-Frame-Mounting 


Type  F-2  Oil  Circuit-Breaker.  Mul- 
tiple-Single-Pole Single -Throw 
500  - Ampere  7500- Volt,  Indoor 
Hand  - Operated  Remote- 
Control  Pipe-Mounting 


Type  F-3  Oil  Circuit-Breaker.  Three- 
Pole  Single-Throw  800- Ampere  4500- 
Volt,  Indoor  Hand-Operated 
Switchboard  Mounting 

(Tank  Removed) 


Type  F-2  Oil  Circuit  - Breaker,  Three -Pole 
Double-Throw  600-Ampere  7500-Volt,  Hand- 
Operated  Switchboard  Mounting 

(Tank  Removed) 


124 


Switchboards  For  Power  Stations 


1541 


Type  B-2  Oil  Circuit-Breaker.  Four-Pole  Sin- 
gle-Throw 2000-Ampere  7500-Volt,  Hand- 
Operated,  Wall-Mounting  (Tank  Removed) 


Type  B-3  Oil  Circuit-Breaker.  Three-Pole 
Single-Throw  300-Ampere  23,000- Volt, 
Switchboard-Mounting 


Type  E-9  Oil  Circuit-Breaker.  'Phree-Pole 
Single-Throw  1200-Ampere  13,200-Volt, 
Electrically  Operated  Horizontal- 
Pipe- Frame- Mounting 


Type  F-3  Oil  Circuit-Breaker.  Three-Pole  Sin- 
gle-Throw 500-Ampere  13,200-Volt,  Indoor 
Electrically-Operated  Wall-Mounting 
Automatic 


1541 


Switchboards  For  Power  Stations 


125 


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126 


Switchboards  For  Power  Stations 


1541 


Type  C-2  Oil  Circuit-Breaker.  Three-Pole  Electrically-Operated 
Vertically-Arranged  Leads,  2000  Amperes  15000  Volts. 

Front  View  Showing  Breaker  in  Open  Position  With  Two  Doors  and 
One  Tank  Removed.  (Breaker  Shown  Mounted  on  Structure) 


1541 


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Switchboards  For  Power  Stations 


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Switchboards  For  Power  Stations 


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Switchboards  For  Power  Stations 


1541 


Reactance  Type,  300-Ampere,  110,000-Volt  Oil  Circuit-  Three-Pole  Reactance  Type,  1200-Ampere  and  Type  C-1  600-Ampere, 

Breakers  and  Disconnecting  Switches,  Lehigh  15000-Volt  Oil  Circuit-Breakers,  All  in  Same  Structure. 

Navigation  Electric  Co.,  Hauto,  Pa.  Lehigh  Navigation  Electric  Co.,  Hauto,  Pa. 


; Type  CD  Carbon  Circuit-Breaker.  Two-Pole  100-Am- 
i pere  600-Volt  with  Separate  Closing  Handles  and 
Common  Trip,  One  Under-Voltage,  and 
Two  Overload  Tripping  Coils 


j Type  CA  Carbon  Circuit-Breaker.  Three-Pole  8000- 
j Ampere  25-Cycle  500-Volt,  Electrically  Operated 
Non- Automatic 


Type  CA  Carbon  Circuit-Breaker.  Four-Pole  800- 
Ampere  250-Volt  with  Inverse-Time-Element  Dash 
Pots  and  Self-Contained  Reverse-Current 
Tripping  Attachment  on  Two  Outer  Poles 


Type  CA  Carbon  Circuit-Breaker.  Single-Pole  24000- 
Ampere  750-Volt,  Electrically-Operated 


operated  Circuit-Breakers 


1541 


Sivitch hoard's  For  Power  Stations 


133 


Vertical  Switchboard,  Controlling  Incoming  66000-Volt  Line  and  11000-Volt  and 
2400-Volt  Feeders  and  Battery  Charging  Equipment.  Albina 
Substation,  Northwestern  Electric  Co. 


Fifteen  Panel  Switchboard  Controlling  11, 000- Volt  Incoming  Lines  and  Feeders 
and  23000-Volt  Feeders.  Municipal  Plant,  Cleveland,  Ohio 


Switchboards  For  Power  Stations 


1514 


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1541 


Switchboards  For  Power  Stations 


135 


Switchboard  for  Michigan  Northern  Power  Co.,  Sault  Ste  Marie,  Mich.,  Controlling 
4400-Volt  Generators  and  Feeders.  (Two  Generators  Controlled 
from  18-Inch  Wide  Panels) 


Control  Gallery  and  Desks  of  Engleside  Substation,  Edison  Electric  Co.,  Lancaster, 
Pa.  Desks  from  Left  to  Right  are  11000-Volt,  60  Cycle;  11000-Volt  25-Cycle; 
2300  Volt,  25-Cycle.  Vertical  Board  Contains  Local  Service  and 
Recording  Meters.  Battery  Charging  Set 
Shown  in  Foreground 


WESTINGHOUSE  ELECTRIC  & MFC.  CO. 

EAST  PITTSBURGH,  PA. 

DISTRICT  SALES  OFFICES 


City  Building  Street 

ATLANTA.  GA.  . . . Candler 127  Peachtree 

BALTIMORE,  MD.  . . Westinghouse 121  E,  Baltimore 

BIRMINGHAM,  ALA.  . . Brown-Marx 1st  Ave.  and  20th 

BLUEFIELD,  W.  VA.  . Kelley-Moyer  ....  Raleigh  & Higginbotham  Ave. 

BOSTON,  MASS.  . . Rice 10  High 

BUFFALO,  N.  Y.  . . Ellicott  Square Ellicott  Square 

BUTTE,  MONT.  . . . Montana  Electric  Co  ...  . 50-52  East  Broadway 

CHARLESTON.  W.  VA.  . Union  Trust 

CHARLOTTE,  N.  C.  . . Commercial  Bank,  Rooms  409-10-1 1 Cor.  Tryon  & Fourth 

CHATTANOOGA,  TENN.  . Hamilton  National  Bank 

CHICAGO,  ILL.  . Conway 1 1 1 W.Washington 

CINCINNATI,  O.  . . . Traction 5th  & Walnut 

CLEVELAND,  O.  . . Swetland 1010  Euclid  Ave. 

COLUMBUS,  O . . . Interurban  Terminal 3rd  & Rich 

^DALLAS,  TEX.  . Cotton  Exchange Akard  & Wood 

DENVER,  COL.  Gas  & Electric 910  15th 

DES  MOINES,  I A.  . , Fleming  . 21634  6th  Ave. 

DAYTON.  O.  ...  Reibold  Main 

DETROIT,  MICH.  . . Dime  Savings  Bank Fort  & Griswold 

*EL  PASO,  TEX.  . Mills  . ' Oregon  & Mills 

INDIANAPOLIS,  IND.  . . Traction  Terminal Illinois  & Market 

JOPLIN,  MO.  BaSom 418  Joplin 

KANSAS  CITY,  MO.  . Orear-Leslie 1012  Baltimore  Ave. 

LOUISVILLE,  KY.  . . Paul  Jones 312  4th  Ave. 

LOS  ANGELES,  CAL.  . I.  N.  Van  Nuys  . . ' . . 7th  & Spring 

MEMPHIS.  TENN.  . Exchange 6 N.  2nd 

MILWAUKEE,  WIS.  . First  National  Bank 425  E.  Water 

MINNEAPOLIS,  MINN.  Met.  Life  Insurance 119-131  S.  3rd 

NEW  ORLEANS,  LA.  . Maison  Blanche 921  Canal 

NEW  YORK,  N.  Y.  . . City  Investing 165  Broadway 

PHILADELPHIA,  PA.  . . Widener 1325-1329  Chestnut 

PITTSBURGH,  PA.  . Union  Bank 306  Wood 

PORTLAND,  ORE.  . Northwestern  Bank  ....  Broadway  & Morrison 

ROCHESTER,  N.  Y.  . Chamber  of  Commerce 1 19  E.  Main 

ST.  LOUIS,  MO 300  N.  Broadway 

SALT  LAKE  CITY,  UTAH  . Walker  Bank 2d,  South  & Main 

SAN  FRANCISCO,  CAL.  . Electric 165  Second 

SEATTLE,  WASH.  Alaska 2nd  and  Cherry 

SYRACUSE,  N.  Y.  . . University 120  Vanderbilt  Square 

TOLEDO,  O Ohio '.  . • Madison  Ave.  & Superior 

WASHINGTON.  D.  C.  . . Hibbs 723  15th  N.  W. 

WILKES-BARRE,  PA.  Miners’  Bank 

*W.  E & M.  Co.  of  Texas. 


Service  Department  Repair  Shops 

Ati..\nta,  Ga.  Mangum  and  Markham  Streets  New  York,  N.  Y.  . .512  West  23d  Street 

Boston,  Mass.  . . 37  Wormwood  Street  Phil.;  oelphia.  Pa.  214-220  North  22nd  Street 

Buffalo,  N.  Y.  . . 6 and  8 Lock  Street  Pitt:  burgh.  Pa.,  Arnberson  Ave.  & P.  R.  R. 

Chicago,  III.  . . . 32  So.  Peoria  Street  S.\n  'rancisco.  Cal.  . 1400  PMurth  St. 

Los  Angeles,  Cal.  . . 2026  Bay  Street  Seattli.  Wash.  . 560  First  Ave.,  South 


WESTINGHOUSE  ELECTRIC  EXPORT  COMPANY 

NEW  YORK  OFFICE— 165  Broadway,  New  York  C’Ty,  N.  Y. 

London  Office — No.  2 Norfolk  Street  Strand 

Japan — Takata  & Company,  Tokio 
Chile — J.  K.  Robinson,  Iquique,  Chile 
Brazil — F.  H.  Walter  & Co.,  Rio  de  Janeiro,  for  Northern  Brazil 
Byington  & Co.,  Sao  Paulo  for  Southern  Brazil 
Colombia — Vincente  B.  Villa,  Medellin 

Venezuela — H.  I.  Skilton,  520  National  Bank  of  Cuba  Building,  Havana,  Cuba 
Porto  Rico — Porto  Rico  Railway,  Light  & Power  Co.,  San  Juan,  Porto  Rico 
Cuba — Westinghouse  Electric  Export  Co. 

520  National  Bank  of  Cuba  Building,  Havana,  Cuba. 

Co.STA  Rica  and  Nicaragua — Purdy  Engineering  Co.,  San  Jose,  Costa  Rica 
Salvador — W.  C.  McEntee,  Santa  Ana,  Salvador 
European  and  Asiatic  Russia — Russian  Electric  Co.,  Dynamo,  Petrograd,  Russia 
Mexico — Compania  Ingeniera,  Importadora  y Cnntratista,  S.  A.,  City  of  Mexico 
(Successors  to  G.  & O.  Braniff  & Co.) 

FOREIGN  COMPANIES 

Canadian  Westinghouse  Company,  Ltd.,  Hamilton,  Ontario 
The  British  Westinghouse  Electric  & Manufacturing  Company,  Ltd.,  Manchester,  England 
For  the  United  Kingdom  and  her  Colonies  (except  Canada)  Germany,  Austria  and  Russia 
Westinghouse  Norsk  Elektrisk  Aktieselskap — Prinsens  Gate  21,  Kristiania,  Norway 
For  Norway  and  Sweden 

SociETE  Anonye  Westingpouse,  Paris,  France 
For  France,  Belgium,  Spain,  Holland,  Switzerland,  Portugal,  their  colonies  and  countries 
under  their  protectorate 

The  Westinghouse  Electric  Company,  Ltd.,  Norfolk  Street,  .Strand,  London,  W.  C. 
gociETA  Italiana  Westinghouse,  Vado  Ligure,  Italy 
For  Italy 


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